Backend:

-Generalize SFTP query param option map building
-Add "key" and "phrase" as SFTP query params
  key: custom private key name
  phrase: passphrase used to unlock key
-Add CRUD support for custom private keys
  Key files are stored in "user_keys" subdirectory
  File names are constructed by (sanitized) key name
  Basic support for private key content validation
-Existing and new key-related functionality moved into
  SftpPublicPrivateKeyUtils class

UI:
-Add custom private key support to SFTP Credentials dialog
  Add a new auth mode item (authModeSpinner)
  Add Spinner showing saved private key names, with an option
   to create a new one (top).
  Add Delete Private Key button; deletes the selected key
   in Spinner

Testing:
-Add custom private key CRUD support to JavaFileStorageTest app
 via file chooser SFTP Credentials panel

src/java/JavaFileStorage/app/src/main/java/keepass2android/javafilestorage/SftpPublicPrivateKeyUtils.java

@@ -0,0 +1,216 @@
+package keepass2android.javafilestorage;
+
+import android.util.Pair;
+
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.StringReader;
+import java.util.regex.Pattern;
+
+import androidx.annotation.Nullable;
+
+import com.jcraft.jsch.JSch;
+import com.jcraft.jsch.JSchException;
+import com.jcraft.jsch.KeyPair;
+
+class SftpPublicPrivateKeyUtils {
+
+    private enum Validity {
+        NOT_ATTEMPTED, VALID, NOT_VALID;
+    }
+
+    private static final String SFTP_CUSTOM_KEY_DIRNAME = "user_keys";
+
+    private static final String KP2A_PRIVATE_KEY_FILENAME = "id_kp2a_rsa";
+
+    private final File appBaseDir;
+
+    /**
+     * Do NOT access this variable directly! Use {@link #baseDir()} instead.
+     */
+    private final File customKeyBaseDir;
+    private volatile Validity validDir = Validity.NOT_ATTEMPTED;
+
+    SftpPublicPrivateKeyUtils(String appBaseDir) {
+        // Assume app base directory exists already
+        this.appBaseDir = new File(appBaseDir);
+
+        // Intentionally skipping existence/creation checking in constructor
+        // See baseDir()
+        this.customKeyBaseDir = new File(appBaseDir, SFTP_CUSTOM_KEY_DIRNAME);
+    }
+
+    private Pair<File, Boolean> baseDir() {
+        if (validDir == Validity.NOT_ATTEMPTED) {
+            synchronized (this) {
+                if (!customKeyBaseDir.exists()) {
+                    customKeyBaseDir.mkdirs();
+                }
+                if (customKeyBaseDir.exists() && customKeyBaseDir.isDirectory()) {
+                    validDir = Validity.VALID;
+                } else {
+                    validDir = Validity.NOT_VALID;
+                }
+            }
+        }
+        return new Pair<>(customKeyBaseDir, validDir == Validity.VALID);
+    }
+
+    boolean deleteCustomKey(String keyName) throws FileNotFoundException {
+        File f = getCustomKeyFile(keyName);
+        return f.isFile() && f.delete();
+    }
+
+    String[] getCustomKeyNames() {
+        Pair<File, Boolean> base = baseDir();
+        if (!base.second) {
+            // Log it?
+            return new String[]{};
+        }
+        return base.first.list();
+    }
+
+    void savePrivateKeyContent(String keyName, String keyContent) throws IOException, Exception {
+        keyContent = PrivateKeyValidator.ensureValidContent(keyContent);
+
+        File f = getCustomKeyFile(keyName);
+        try (BufferedWriter w = new BufferedWriter(new FileWriter(f))) {
+            w.write(keyContent);
+        }
+    }
+
+    String getCustomKeyFilePath(String customKeyName) throws FileNotFoundException {
+        return getCustomKeyFile(customKeyName).getAbsolutePath();
+    }
+
+    String resolveKeyFilePath(JSch jschInst, @Nullable String customKeyName) {
+        // Custom private key configured
+        if (customKeyName != null) {
+            try {
+                return getCustomKeyFilePath(customKeyName);
+            } catch (FileNotFoundException e) {
+                System.out.println(e);
+            }
+        }
+        // Use KP2A's public/private key
+        String keyFilePath = getAppKeyFileName();
+        try{
+            createKeyPair(jschInst, keyFilePath);
+        } catch (Exception ex) {
+            System.out.println(ex);
+        }
+        return keyFilePath;
+    }
+
+    String createKeyPair(JSch jschInst) throws IOException, JSchException {
+        return createKeyPair(jschInst, getAppKeyFileName());
+    }
+
+    /**
+     * Exposed for testing purposes only
+     * @param keyName
+     * @return
+     */
+    String getSanitizedCustomKeyName(String keyName) {
+        return PrivateKeyValidator.sanitizeKeyAsFilename(keyName);
+    }
+
+    /**
+     * Exposed for testing purposes only.
+     * @param keyContent
+     * @return
+     * @throws Exception
+     */
+    String getValidatedCustomKeyContent(String keyContent) throws Exception {
+        return PrivateKeyValidator.ensureValidContent(keyContent);
+    }
+
+    private String createKeyPair(JSch jschInst, String key_filename) throws JSchException, IOException {
+        String public_key_filename = key_filename + ".pub";
+        File file = new File(key_filename);
+        if (file.exists())
+            return public_key_filename;
+        int type = KeyPair.RSA;
+        KeyPair kpair = KeyPair.genKeyPair(jschInst, type, 4096);
+        kpair.writePrivateKey(key_filename);
+
+        kpair.writePublicKey(public_key_filename, "generated by Keepass2Android");
+        //ret = "Fingerprint: " + kpair.getFingerPrint();
+        kpair.dispose();
+        return public_key_filename;
+    }
+
+    private String getAppKeyFileName() {
+        return new File(appBaseDir, KP2A_PRIVATE_KEY_FILENAME).getAbsolutePath();
+    }
+
+    private File getCustomKeyFile(String customKeyName) throws FileNotFoundException {
+        Pair<File, Boolean> base = baseDir();
+        if (!base.second) {
+            throw new FileNotFoundException("Custom key directory");
+        }
+
+        String keyFileName = PrivateKeyValidator.sanitizeKeyAsFilename(customKeyName);
+        if (!keyFileName.isEmpty()) {
+            File keyFile = new File(base.first, keyFileName);
+            // Protect against bad actors trying to navigate away from the base directory.
+            // This is probably overkill, given sanitizeKeyAsFilename(...) but better safe than sorry.
+            if (base.first.equals(keyFile.getParentFile())) {
+                return keyFile;
+            }
+        }
+        // The key was sanitized to nothing, or the parent check above failed.
+        throw new FileNotFoundException("Malformed key name");
+    }
+
+
+    private static class PrivateKeyValidator {
+        private static final Pattern CONTENT_FIRST_LINE = Pattern.compile("^-+BEGIN\\s[^\\s]+\\sPRIVATE\\sKEY-+$");
+        private static final Pattern CONTENT_LAST_LINE = Pattern.compile("^-+END\\s[^\\s]+\\sPRIVATE\\sKEY-+$");
+
+        /**
+         * Key-to-filename sanitizer solution sourced from:
+         *  <a href="https://www.b4x.com/android/forum/threads/sanitize-filename.82558/" />
+         */
+        private static final Pattern KEY_SANITIZER = Pattern.compile("([^\\p{L}\\s\\d\\-_~,;:\\[\\]\\(\\).'])",
+                Pattern.CASE_INSENSITIVE);
+
+        static String sanitizeKeyAsFilename(String key) {
+            return KEY_SANITIZER.matcher(key.trim()).replaceAll("");
+        }
+
+        static String ensureValidContent(String content) throws Exception {
+            content = content.trim();
+
+            boolean isValid = true;
+            try (BufferedReader r = new BufferedReader(new StringReader(content))) {
+                boolean validFirst = false;
+                String line;
+                String last = null;
+                while ((line = r.readLine()) != null) {
+                    if (!validFirst) {
+                        if (CONTENT_FIRST_LINE.matcher(line).matches()) {
+                            validFirst = true;
+                        } else {
+                            isValid = false;
+                            break;
+                        }
+                    }
+                    last = line;
+                }
+                if (!isValid || last == null || !CONTENT_LAST_LINE.matcher(last).matches()) {
+                    throw new RuntimeException("Malformed private key content");
+                }
+            } catch (Exception e) {
+                android.util.Log.d(SftpStorage.class.getName(), "Invalid key content", e);
+                throw e;
+            }
+
+            return content;
+        }
+    }
+}

src/java/JavaFileStorage/app/src/main/java/keepass2android/javafilestorage/SftpStorage.java

@@ -2,7 +2,6 @@ package keepass2android.javafilestorage;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
-import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
@@ -20,7 +19,6 @@ import com.jcraft.jsch.ChannelSftp;
 import com.jcraft.jsch.ChannelSftp.LsEntry;
 import com.jcraft.jsch.JSch;
 import com.jcraft.jsch.JSchException;
-import com.jcraft.jsch.KeyPair;
 import com.jcraft.jsch.Session;
 import com.jcraft.jsch.SftpATTRS;
 import com.jcraft.jsch.SftpException;
@@ -30,11 +28,32 @@ import android.content.Context;
 import android.content.Intent;
 import android.os.Bundle;
 
+@SuppressWarnings("unused")  // Exposed by JavaFileStorageBindings
 public class SftpStorage extends JavaFileStorageBase {
+	@FunctionalInterface
+	interface ValueResolver<T> {
+		/**
+		 * Takes a raw value and resolves it to either a String containing the String representation
+		 * of that value, or null. The latter signifying that the raw value could not be "resolved".
+		 *
+		 * @param value
+		 * @return String, or null if not resolvable
+		 */
+		String resolve(T value);
+	}
 
 	public static final int DEFAULT_SFTP_PORT = 22;
 	public static final int UNSET_SFTP_CONNECT_TIMEOUT = -1;
 	private static final String SFTP_CONNECT_TIMEOUT_OPTION_NAME = "connectTimeout";
+	private static final String SFTP_KEYNAME_OPTION_NAME = "key";
+	private static final String SFTP_KEYPASSPHRASE_OPTION_NAME = "phrase";
+
+	private static final ValueResolver<Integer> cTimeoutResolver = c ->
+			c == null || c == UNSET_SFTP_CONNECT_TIMEOUT ? null : String.valueOf(c);
+
+	private static final ValueResolver<String> nonBlankStringResolver = s ->
+			s == null || s.isBlank() ? null : s;
+
 
 	JSch jsch;
 
@@ -44,39 +63,36 @@ public class SftpStorage extends JavaFileStorageBase {
 		public String username;
 		public String password;
 		public String localPath;
+		public String keyName;
+		public String keyPassphrase;
 		public int port;
 		public int connectTimeoutSec = UNSET_SFTP_CONNECT_TIMEOUT;
 
 
 		public String toString() {
 			return "ConnectionInfo{host=" + host + ",port=" + port + ",user=" + username +
-					",pwd=<hidden>,path=" + localPath + ",connectTimeout=" + connectTimeoutSec +
+					",pwd=<hidden>,localPath=" + localPath + ",key=" + keyName +
+					",phrase=<hidden>,connectTimeout=" + connectTimeoutSec +
 					"}";
 		}
+	}
 
-		boolean hasOptions() {
-			return connectTimeoutSec != UNSET_SFTP_CONNECT_TIMEOUT;
+	private static Map<String, String> buildOptionMap(ConnectionInfo ci, boolean includeSensitive) {
+		OptionMapBuilder b = new OptionMapBuilder()
+				.addOption(SFTP_CONNECT_TIMEOUT_OPTION_NAME, ci.connectTimeoutSec, cTimeoutResolver)
+				.addOption(SFTP_KEYNAME_OPTION_NAME, ci.keyName, nonBlankStringResolver);
+		if (includeSensitive) {
+			b.addOption(SFTP_KEYPASSPHRASE_OPTION_NAME, ci.keyPassphrase, nonBlankStringResolver);
 		}
+		return b.build();
 	}
 
-	private static Map<String, String> buildOptionMap(ConnectionInfo ci) {
-		return buildOptionMap(ci.connectTimeoutSec);
-	}
-
-	private static Map<String, String> buildOptionMap(int connectTimeoutSec) {
-		Map<String, String> opts = new HashMap<>();
-		if (connectTimeoutSec != UNSET_SFTP_CONNECT_TIMEOUT) {
-			opts.put(SFTP_CONNECT_TIMEOUT_OPTION_NAME, String.valueOf(connectTimeoutSec));
-		}
-		return opts;
-	}
-
-
 	Context _appContext;
+	private final SftpPublicPrivateKeyUtils _keyUtils;
 
 	public SftpStorage(Context appContext) {
 		_appContext = appContext;
-
+		_keyUtils = new SftpPublicPrivateKeyUtils(getBaseDir());
 	}
 
 	private static final String SFTP_PROTOCOL_ID = "sftp";
@@ -184,7 +200,8 @@ public class SftpStorage extends JavaFileStorageBase {
 			tryDisconnect(c);
 
 			return buildFullPath(cInfo.host, cInfo.port, newPath,
-					cInfo.username, cInfo.password, cInfo.connectTimeoutSec);
+					cInfo.username, cInfo.password, cInfo.connectTimeoutSec,
+					cInfo.keyName, cInfo.keyPassphrase);
 		} catch (Exception e) {
 			throw convertException(e);
 		}
@@ -402,28 +419,23 @@ public class SftpStorage extends JavaFileStorageBase {
 		return java.net.URLEncoder.encode(unencoded, UTF_8);
 	}
 
+
 	ChannelSftp init(ConnectionInfo cInfo) throws JSchException, UnsupportedEncodingException {
 		jsch = new JSch();
 
 		String base_dir = getBaseDir();
 		jsch.setKnownHosts(base_dir + "/known_hosts");
 
-		String key_filename = getKeyFileName();
-		try{
-			createKeyPair(key_filename);
-		} catch (Exception ex) {
-			System.out.println(ex);
-		}
+		String key_filepath = _keyUtils.resolveKeyFilePath(jsch, cInfo.keyName);
 
 		try {
-			jsch.addIdentity(key_filename);
-		} catch (java.lang.Exception e)
-		{
+			jsch.addIdentity(key_filepath);
+		} catch (java.lang.Exception e) {
 
 		}
 
 		Session session = jsch.getSession(cInfo.username, cInfo.host, cInfo.port);
-		UserInfo ui = new SftpUserInfo(cInfo.password, _appContext);
+		UserInfo ui = new SftpUserInfo(cInfo.password, cInfo.keyPassphrase, _appContext);
 		session.setUserInfo(ui);
 
 		session.setConfig("PreferredAuthentications", "publickey,password");
@@ -434,7 +446,6 @@ public class SftpStorage extends JavaFileStorageBase {
 		channel.connect();
 		ChannelSftp c = (ChannelSftp) channel;
 
-		logDebug("success: init Sftp");
 		return c;
 
 	}
@@ -451,38 +462,60 @@ public class SftpStorage extends JavaFileStorageBase {
 		return _appContext.getFilesDir().getAbsolutePath();
 	}
 
-	private String getKeyFileName() {
-		return getBaseDir() + "/id_kp2a_rsa";
+	public boolean deleteCustomKey(String keyName) throws FileNotFoundException {
+		return _keyUtils.deleteCustomKey(keyName);
 	}
 
+	public String[] getCustomKeyNames() {
+		return _keyUtils.getCustomKeyNames();
+	}
+
+	@SuppressWarnings("unused")  // Exposed by JavaFileStorageBindings
 	public String createKeyPair() throws IOException, JSchException {
-		return createKeyPair(getKeyFileName());
-
+		return _keyUtils.createKeyPair(jsch);
 	}
 
-	private String createKeyPair(String key_filename) throws JSchException, IOException {
-		String public_key_filename = key_filename + ".pub";
-		File file = new File(key_filename);
-		if (file.exists())
-			return public_key_filename;
-		int type = KeyPair.RSA;
-		KeyPair kpair = KeyPair.genKeyPair(jsch, type, 4096);
-		kpair.writePrivateKey(key_filename);
-
-		kpair.writePublicKey(public_key_filename, "generated by Keepass2Android");
-		//ret = "Fingerprint: " + kpair.getFingerPrint();
-		kpair.dispose();
-		return public_key_filename;
 
+	@SuppressWarnings("unused")  // Exposed by JavaFileStorageBindings
+	public void savePrivateKeyContent(String keyName, String keyContent) throws IOException, Exception {
+		_keyUtils.savePrivateKeyContent(keyName, keyContent);
 	}
 
+	/**
+	 * Exposed for testing purposes only.
+	 * @param keyName
+	 * @return
+	 */
+	public String sanitizeCustomKeyName(String keyName) {
+		return _keyUtils.getSanitizedCustomKeyName(keyName);
+	}
+
+	/**
+	 * Exposed for testing purposes only.
+	 * @param keyContent
+	 * @return
+	 * @throws Exception
+	 */
+	public String getValidatedCustomKeyContent(String keyContent) throws Exception {
+		return _keyUtils.getValidatedCustomKeyContent(keyContent);
+	}
+
+
 	public ConnectionInfo splitStringToConnectionInfo(String filename)
 			throws UnsupportedEncodingException {
 		ConnectionInfo ci = new ConnectionInfo();
 		ci.host = extractUserPwdHostPort(filename);
+
 		String userPwd = ci.host.substring(0, ci.host.indexOf('@'));
-		ci.username = decode(userPwd.substring(0, userPwd.indexOf(":")));
-		ci.password = decode(userPwd.substring(userPwd.indexOf(":")+1));
+		int sepIdx = userPwd.indexOf(":");
+		if (sepIdx > 0) {
+			ci.username = decode(userPwd.substring(0, sepIdx));
+			ci.password = decode(userPwd.substring(sepIdx + 1));
+		} else {
+			ci.username = userPwd;
+			ci.password = null;
+		}
+
 		ci.host = ci.host.substring(ci.host.indexOf('@') + 1);
 		ci.port = DEFAULT_SFTP_PORT;
 		int portSeparatorIndex = ci.host.indexOf(":");
@@ -503,6 +536,12 @@ public class SftpStorage extends JavaFileStorageBase {
 				logDebug(SFTP_CONNECT_TIMEOUT_OPTION_NAME + " option not a number: " + optVal);
 			}
 		}
+		if (options.containsKey(SFTP_KEYNAME_OPTION_NAME)) {
+			ci.keyName = options.get(SFTP_KEYNAME_OPTION_NAME);
+		}
+		if (options.containsKey(SFTP_KEYPASSPHRASE_OPTION_NAME)) {
+			ci.keyPassphrase = options.get(SFTP_KEYPASSPHRASE_OPTION_NAME);
+		}
 		return ci;
 	}
 
@@ -544,9 +583,7 @@ public class SftpStorage extends JavaFileStorageBase {
 					.append("@")
 					.append(ci.host)
 					.append(ci.localPath);
-			if (ci.hasOptions()) {
-				appendOptions(dName, buildOptionMap(ci));
-			}
+			appendOptions(dName, buildOptionMap(ci, false));
 			return dName.toString();
 		}
 		catch (Exception e)
@@ -580,11 +617,15 @@ public class SftpStorage extends JavaFileStorageBase {
 
 	public String buildFullPath(String host, int port, String localPath,
 										String username, String password,
-										int connectTimeoutSec)
+										int connectTimeoutSec,
+										String keyName, String keyPassphrase)
 			throws UnsupportedEncodingException {
-		StringBuilder uri = new StringBuilder(getProtocolPrefix())
-				.append(encode(username)).append(":").append(encode(password))
-				.append("@").append(host);
+
+		StringBuilder uri = new StringBuilder(getProtocolPrefix()).append(encode(username));
+		if (password != null) {
+			uri.append(":").append(encode(password));
+		}
+		uri.append("@").append(host);
 
 		if (port != DEFAULT_SFTP_PORT) {
 			uri.append(":").append(port);
@@ -593,8 +634,11 @@ public class SftpStorage extends JavaFileStorageBase {
 			uri.append(localPath);
 		}
 
-		Map<String, String> opts = buildOptionMap(connectTimeoutSec);
-		appendOptions(uri, opts);
+		appendOptions(uri, new OptionMapBuilder()
+				.addOption(SFTP_CONNECT_TIMEOUT_OPTION_NAME, connectTimeoutSec, cTimeoutResolver)
+				.addOption(SFTP_KEYNAME_OPTION_NAME, keyName, nonBlankStringResolver)
+				.addOption(SFTP_KEYPASSPHRASE_OPTION_NAME, keyPassphrase, nonBlankStringResolver)
+				.build());
 
 		return uri.toString();
 	}
@@ -635,4 +679,31 @@ public class SftpStorage extends JavaFileStorageBase {
 			return o1.getKey().compareTo(o2.getKey());
 		}
 	}
+
+	private static class OptionMapBuilder {
+		private final Map<String, String> options = new HashMap<>();
+
+		/**
+		 * Attempts to add a raw value <code>oVal</code> to the underlying option map with key <code>oName</code>
+		 * iff the <code>resolver</code> produces a non-null output when invoked using the raw value.
+		 *
+		 * @param oName the name/key associated with the value, if added
+		 * @param oVal the raw value attempting to be added
+		 * @param resolver the resolver that determines if the value will be added
+		 *
+		 * @return OptionMapBuilder (updated)
+		 * @param <T> the raw value type
+		 */
+		<T> OptionMapBuilder addOption(final String oName, T oVal, ValueResolver<T> resolver) {
+			String resolved = resolver.resolve(oVal);
+			if (resolved != null) {
+				options.put(oName, resolved);
+			}
+			return this;
+		}
+
+		Map<String, String> build() {
+			return new HashMap<>(options);
+		}
+	}
 }

src/java/JavaFileStorage/app/src/main/java/keepass2android/javafilestorage/SftpUserInfo.java

@@ -113,17 +113,19 @@ public class SftpUserInfo implements UserInfo {
 	Context _appContext;
 
 	String _password;
+	String _passphrase;
 	
-	public SftpUserInfo(String password, Context appContext)
+	public SftpUserInfo(String password, String passphrase, Context appContext)
 	{
 		_password = password;
+		_passphrase = passphrase;
 		_appContext = appContext;
 	}
 
 	@Override
 	public String getPassphrase() {
-		
-		return null;
+
+		return _passphrase;
 	}
 
 	@Override
@@ -134,12 +136,12 @@ public class SftpUserInfo implements UserInfo {
 
 	@Override
 	public boolean promptPassword(String message) {
-		return true;
+		return _password != null;
 	}
 
 	@Override
 	public boolean promptPassphrase(String message) {
-		return false; //passphrase not supported
+		return _passphrase != null;
 	}
 
 	@Override

src/java/JavaFileStorageTest-AS/app/src/main/java/com/crocoapps/javafilestoragetest2/MainActivity.java

@@ -697,12 +697,11 @@ public class MainActivity extends Activity implements JavaFileStorage.FileStorag
 		if (protocolId.equals("sftp"))
 		{
 			final View view = getLayoutInflater().inflate(R.layout.sftp_credentials, null);
+			final SftpStorage sftpStorage = (SftpStorage)storageToTest;
 
 			view.findViewById(R.id.send_public_key).setOnClickListener(v -> {
 				Intent sendIntent = new Intent();
 
-
-                SftpStorage sftpStorage = (SftpStorage)storageToTest;
                 try {
                     String pub_filename = sftpStorage.createKeyPair();
 
@@ -715,51 +714,121 @@ public class MainActivity extends Activity implements JavaFileStorage.FileStorag
                 }
                 catch (Exception ex)
                 {
-                    Toast.makeText(this,"Failed to create key pair: " + ex.getMessage(), Toast.LENGTH_LONG);
-                    return;
+                    Toast.makeText(this,"Failed to create key pair: " + ex.getMessage(), Toast.LENGTH_LONG).show();
                 }
-
-
 			});
+
+			view.findViewById(R.id.list_private_keys).setOnClickListener(v -> {
+				String[] keys = sftpStorage.getCustomKeyNames();
+				Toast.makeText(this, "keys: " + String.join(",", keys), Toast.LENGTH_LONG).show();
+			});
+
+			view.findViewById(R.id.add_private_key).setOnClickListener(v -> {
+				EditText etKeyName = view.findViewById(R.id.private_key_name);
+				String keyName = etKeyName.getText().toString();
+				EditText etKeyContent = view.findViewById(R.id.private_key_content);
+				String keyContent = etKeyContent.getText().toString();
+
+				try {
+					sftpStorage.savePrivateKeyContent(keyName, keyContent);
+					Toast.makeText(this, "Add successful", Toast.LENGTH_LONG).show();
+				}
+				catch (Exception e) {
+					Toast.makeText(this, "Add failed: " + e.getMessage(), Toast.LENGTH_LONG).show();
+				}
+			});
+
+			view.findViewById(R.id.delete_private_key).setOnClickListener(v -> {
+				EditText etKeyName = view.findViewById(R.id.private_key_name);
+				String keyName = etKeyName.getText().toString();
+
+				String exMessage = null;
+				boolean success = false;
+				try {
+					success = sftpStorage.deleteCustomKey(keyName);
+				}
+				catch (Exception e) {
+					exMessage = e.getMessage();
+				}
+				StringBuilder msg = new StringBuilder("Delete ");
+				msg.append(success ? "succeeded" : "FAILED");
+				if (exMessage != null) {
+					msg.append(" (").append(exMessage).append(")");
+				}
+				Toast.makeText(this, msg.toString(), Toast.LENGTH_LONG).show();
+			});
+
+			view.findViewById(R.id.validate_private_key).setOnClickListener(v -> {
+				EditText etKeyName = view.findViewById(R.id.private_key_name);
+				String inKeyName = etKeyName.getText().toString();
+
+				if (!inKeyName.isEmpty()) {
+					String keyResponse;
+					try {
+						keyResponse = sftpStorage.sanitizeCustomKeyName(inKeyName);
+					} catch (Exception e) {
+						keyResponse = "EX:" + e.getMessage();
+					}
+					String msg = "key: [" + inKeyName + "] -> [" + keyResponse + "]";
+					Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
+				}
+
+				EditText etKeyContent = view.findViewById(R.id.private_key_content);
+				String inKeyContent = etKeyContent.getText().toString();
+				String msg;
+				if (!inKeyContent.isEmpty()) {
+					try {
+						// We could print the key, but I don't it's that helpful
+						sftpStorage.getValidatedCustomKeyContent(inKeyContent);
+						msg = "Key content is valid";
+					} catch (Exception e) {
+						msg = "Invalid key content: " + e.getMessage();
+					}
+					Toast.makeText(this, msg, Toast.LENGTH_LONG).show();
+				}
+			});
+
 			new AlertDialog.Builder(this)
 					.setView(view)
 					.setTitle("Enter SFTP credentials")
-					.setPositiveButton("OK",new DialogInterface.OnClickListener() {
+					.setPositiveButton("OK", (dialog, which) -> {
 
-						@Override
-						public void onClick(DialogInterface dialog, int which) {
+						Toast.makeText(MainActivity.this, "Hey", Toast.LENGTH_LONG).show();
 
-							Toast.makeText(MainActivity.this, "Hey", Toast.LENGTH_LONG).show();
-
-							SftpStorage sftpStorage = (SftpStorage)storageToTest;
-							try {
-								EditText etHost = ((EditText)view.findViewById(R.id.sftp_host));
-								String host = etHost.getText().toString();
-								EditText etUser = ((EditText)view.findViewById(R.id.sftp_user));
-								String user = etUser.getText().toString();
-								EditText etPwd = ((EditText)view.findViewById(R.id.sftp_password));
-								String pwd = etPwd.getText().toString();
-								EditText etPort = ((EditText)view.findViewById(R.id.sftp_port));
-								int port = Integer.parseInt(etPort.getText().toString());
-								EditText etInitDir = ((EditText)view.findViewById(R.id.sftp_initial_dir));
-								String initialDir = etInitDir.getText().toString();
-								EditText etConnectTimeout = ((EditText)view.findViewById(R.id.sftp_connect_timeout));
-								int connectTimeout = SftpStorage.UNSET_SFTP_CONNECT_TIMEOUT;
-								String ctStr = etConnectTimeout.getText().toString();
-								if (!ctStr.isEmpty()) {
-									try {
-										int ct = Integer.parseInt(ctStr);
-										if (connectTimeout != ct) {
-											connectTimeout = ct;
-										}
-									} catch (NumberFormatException parseEx) {
+						SftpStorage sftpStorage1 = (SftpStorage)storageToTest;
+						try {
+							EditText etHost = view.findViewById(R.id.sftp_host);
+							String host = etHost.getText().toString();
+							EditText etUser = view.findViewById(R.id.sftp_user);
+							String user = etUser.getText().toString();
+							EditText etPwd = view.findViewById(R.id.sftp_password);
+							String pwd = etPwd.getText().toString();
+							EditText etPort = view.findViewById(R.id.sftp_port);
+							int port = Integer.parseInt(etPort.getText().toString());
+							EditText etInitDir = view.findViewById(R.id.sftp_initial_dir);
+							String initialDir = etInitDir.getText().toString();
+							EditText etConnectTimeout = view.findViewById(R.id.sftp_connect_timeout);
+							int connectTimeout = SftpStorage.UNSET_SFTP_CONNECT_TIMEOUT;
+							String ctStr = etConnectTimeout.getText().toString();
+							if (!ctStr.isEmpty()) {
+								try {
+									int ct = Integer.parseInt(ctStr);
+									if (connectTimeout != ct) {
+										connectTimeout = ct;
 									}
+								} catch (NumberFormatException parseEx) {
 								}
-								onReceivePathForFileSelect(requestCode, sftpStorage.buildFullPath( host, port, initialDir, user, pwd, connectTimeout));
-							} catch (UnsupportedEncodingException e) {
-								// TODO Auto-generated catch block
-								e.printStackTrace();
 							}
+							EditText etKeyName = view.findViewById(R.id.private_key_name);
+							String keyName = etKeyName.getText().toString();
+							EditText etKeyPassphrase = view.findViewById(R.id.private_key_passphrase);
+							String keyPassphrase = etKeyPassphrase.getText().toString();
+
+							onReceivePathForFileSelect(requestCode, sftpStorage1.buildFullPath(
+									host, port, initialDir, user, pwd, connectTimeout,
+									keyName, keyPassphrase));
+						} catch (UnsupportedEncodingException e) {
+							e.printStackTrace();
 						}
 					})
 					.create()

src/java/JavaFileStorageTest-AS/app/src/main/res/layout/sftp_credentials.xml

@@ -77,5 +77,59 @@
 			android:layout_width="fill_parent"
 			android:layout_height="wrap_content"
 			android:text="send public key" />
+		<TextView
+			android:layout_width="fill_parent"
+			android:layout_height="wrap_content"
+			android:gravity="center_horizontal"
+			android:layout_marginTop="20dp"
+			android:textStyle="bold"
+			android:text="Private Keys Functions" />
+
+		<LinearLayout
+			android:orientation="horizontal"
+			android:layout_width="fill_parent"
+			android:layout_height="wrap_content">
+			<Button android:id="@+id/list_private_keys"
+				android:layout_width="fill_parent"
+				android:layout_height="wrap_content"
+				android:layout_weight="1"
+				android:text="List" />
+			<Button android:id="@+id/add_private_key"
+				android:layout_width="fill_parent"
+				android:layout_height="wrap_content"
+				android:layout_weight="1"
+				android:text="Add" />
+			<Button android:id="@+id/delete_private_key"
+				android:layout_width="fill_parent"
+				android:layout_height="wrap_content"
+				android:layout_weight="1"
+				android:text="Delete" />
+			<Button android:id="@+id/validate_private_key"
+				android:layout_width="fill_parent"
+				android:layout_height="wrap_content"
+				android:layout_weight="1"
+				android:text="Validate" />
+		</LinearLayout>
+		<EditText android:id="@+id/private_key_name"
+			android:layout_width="fill_parent"
+			android:layout_height="wrap_content"
+			android:singleLine="true"
+			android:inputType="textNoSuggestions"
+			android:text=""
+			android:hint="key name" />
+		<EditText android:id="@+id/private_key_content"
+			android:layout_width="fill_parent"
+			android:layout_height="wrap_content"
+			android:inputType="textMultiLine"
+			android:lines="5"
+			android:text=""
+			android:hint="key content" />
+		<EditText android:id="@+id/private_key_passphrase"
+			android:layout_width="fill_parent"
+			android:layout_height="wrap_content"
+			android:singleLine="true"
+			android:inputType="textNoSuggestions"
+			android:text=""
+			android:hint="key passphrase (optional)" />
 
 </LinearLayout>

src/keepass2android/FileSelectHelper.cs

@@ -42,6 +42,12 @@ namespace keepass2android
 	    private readonly string _schemeSeparator = "://";
 	    private bool _tryGetPermanentAccess;
 
+		private const int SftpModeSpinnerPasswd = 0;
+		private const int SftpModeSpinnerPubKey = 1;
+		private const int SftpModeSpinnerCustomKey = 2;
+
+		private const int SftpKeySpinnerCreateNewIdx = 0;
+
 	    public string DefaultExtension { get; set; }
 
 		public FileSelectHelper(Activity activity, bool isForSave, bool tryGetPermanentAccess, int requestCode)
@@ -57,81 +63,198 @@ namespace keepass2android
 #if !EXCLUDE_JAVAFILESTORAGE && !NoNet
 			AlertDialog.Builder builder = new AlertDialog.Builder(activity);
 			View dlgContents = activity.LayoutInflater.Inflate(Resource.Layout.sftpcredentials, null);
+			var ctx = activity.ApplicationContext;
+            var fileStorage = new Keepass2android.Javafilestorage.SftpStorage(ctx);
 
-		    var spinner = dlgContents.FindViewById<Spinner>(Resource.Id.sftp_auth_mode_spinner);
-		    dlgContents.FindViewById<Button>(Resource.Id.send_public_key_button).Click += (sender, args) =>
-		    {
-		        var fileStorage = new Keepass2android.Javafilestorage.SftpStorage(activity.ApplicationContext);
-		        string pub_filename = fileStorage.CreateKeyPair();
+            LinearLayout addNewBtn = dlgContents.FindViewById<LinearLayout>(Resource.Id.sftp_add_key_group);
+            Button deleteBtn = dlgContents.FindViewById<Button>(Resource.Id.sftp_delete_key_button);
+            EditText keyNameTxt = dlgContents.FindViewById<EditText>(Resource.Id.sftp_key_name);
+            EditText keyContentTxt = dlgContents.FindViewById<EditText>(Resource.Id.sftp_key_content);
 
-		        Intent sendIntent = new Intent();
-                sendIntent.SetAction(Intent.ActionSend);
-		        sendIntent.PutExtra(Intent.ExtraText, System.IO.File.ReadAllText(pub_filename));
+            var keySpinner = dlgContents.FindViewById<Spinner>(Resource.Id.sftp_key_names);
+			var keyNamesAdapter = new ArrayAdapter(ctx, Android.Resource.Layout.SimpleSpinnerDropDownItem, new List<string>());
+			UpdatePrivateKeyNames(keyNamesAdapter, fileStorage, ctx);
+			keyNamesAdapter.SetDropDownViewResource(Android.Resource.Layout.SimpleSpinnerDropDownItem);
+			keySpinner.Adapter = keyNamesAdapter;
+			keySpinner.SetSelection(SftpKeySpinnerCreateNewIdx);
 
-		        sendIntent.PutExtra(Intent.ExtraSubject, "Keepass2Android sftp public key");
-		        sendIntent.SetType("text/plain");
-		        activity.StartActivity(Intent.CreateChooser(sendIntent, "Send public key to..."));
-            };
+			keySpinner.ItemSelected += (sender, args) =>
+			{
+                if (keySpinner.SelectedItemPosition == SftpKeySpinnerCreateNewIdx)
+				{
+					keyNameTxt.Text = "";
+					keyContentTxt.Text = "";
+					addNewBtn.Visibility = ViewStates.Visible;
+					deleteBtn.Visibility = ViewStates.Gone;
+				}
+				else
+				{
+					addNewBtn.Visibility = ViewStates.Gone;
+					deleteBtn.Visibility = ViewStates.Visible;
+				}
+			};
 
+            var authModeSpinner = dlgContents.FindViewById<Spinner>(Resource.Id.sftp_auth_mode_spinner);
+			dlgContents.FindViewById<Button>(Resource.Id.send_public_key_button).Click += (sender, args) =>
+			{
+                string pub_filename = fileStorage.CreateKeyPair();
 
-            spinner.ItemSelected += (sender, args) =>
-		    {
-		        if (spinner.SelectedItemPosition == 0)
-		        {
-		            dlgContents.FindViewById<EditText>(Resource.Id.sftp_password).Visibility = ViewStates.Visible;
-		            dlgContents.FindViewById<Button>(Resource.Id.send_public_key_button).Visibility = ViewStates.Gone;
-                }
-		        else
-		        {
-		            dlgContents.FindViewById<EditText>(Resource.Id.sftp_password).Visibility = ViewStates.Gone;
-		            dlgContents.FindViewById<Button>(Resource.Id.send_public_key_button).Visibility = ViewStates.Visible;
+				Intent sendIntent = new Intent();
+				sendIntent.SetAction(Intent.ActionSend);
+				sendIntent.PutExtra(Intent.ExtraText, System.IO.File.ReadAllText(pub_filename));
+
+				sendIntent.PutExtra(Intent.ExtraSubject, "Keepass2Android sftp public key");
+				sendIntent.SetType("text/plain");
+				activity.StartActivity(Intent.CreateChooser(sendIntent, "Send public key to..."));
+			};
+
+			dlgContents.FindViewById<Button>(Resource.Id.sftp_save_key_button).Click += (sender, args) =>
+			{
+				string keyName = keyNameTxt.Text;
+				string keyContent = keyContentTxt.Text;
+
+				string toastMsg = null;
+                if (!string.IsNullOrEmpty(keyName) && !string.IsNullOrEmpty(keyContent))
+				{
+					try
+					{
+						fileStorage.SavePrivateKeyContent(keyName, keyContent);
+                        keyNameTxt.Text = "";
+						keyContentTxt.Text = "";
+                        toastMsg = ctx.GetString(Resource.String.private_key_saved);
+                    }
+					catch (Exception e)
+					{
+						toastMsg = ctx.GetString(Resource.String.private_key_save_failed,
+							new Java.Lang.Object[] { e.Message });
+					}
+				}
+				else
+				{
+					toastMsg = ctx.GetString(Resource.String.private_key_info);
+				}
+
+				if (toastMsg!= null) {
+                    Toast.MakeText(_activity, toastMsg, ToastLength.Long).Show();
                 }
+
+				UpdatePrivateKeyNames(keyNamesAdapter, fileStorage, ctx);
+				keySpinner.SetSelection(ResolveKeySpinnerSelection(keyNamesAdapter, keyName));
+			};
+
+			dlgContents.FindViewById<Button>(Resource.Id.sftp_delete_key_button).Click += (sender, args) =>
+			{
+				int selectedKey = dlgContents.FindViewById<Spinner>(Resource.Id.sftp_key_names).SelectedItemPosition;
+				string keyName = ResolveSelectedKeyName(keyNamesAdapter, selectedKey);
+				if (!string.IsNullOrEmpty(keyName))
+				{
+					bool deleted = fileStorage.DeleteCustomKey(keyName);
+
+					int msgId = deleted ? Resource.String.private_key_delete : Resource.String.private_key_delete_failed;
+					string msg = ctx.GetString(msgId, new Java.Lang.Object[] { keyName });
+                    Toast.MakeText(_activity, msg, ToastLength.Long).Show();
+
+					UpdatePrivateKeyNames(keyNamesAdapter, fileStorage, ctx);
+					keySpinner.SetSelection(SftpKeySpinnerCreateNewIdx);
+				}
+			};
+
+			authModeSpinner.ItemSelected += (sender, args) =>
+		    {
+				var passwordBox = dlgContents.FindViewById<EditText>(Resource.Id.sftp_password);
+				var publicKeyButton = dlgContents.FindViewById<Button>(Resource.Id.send_public_key_button);
+				var keyfileGroup = dlgContents.FindViewById<LinearLayout>(Resource.Id.sftp_keyfile_group);
+
+                switch (authModeSpinner.SelectedItemPosition)
+			    {
+				    case SftpModeSpinnerPasswd:
+					    passwordBox.Visibility = ViewStates.Visible;
+					    publicKeyButton.Visibility = ViewStates.Gone;
+					    keyfileGroup.Visibility = ViewStates.Gone;
+					    break;
+				    case SftpModeSpinnerPubKey:
+					    passwordBox.Visibility = ViewStates.Gone;
+					    publicKeyButton.Visibility = ViewStates.Visible;
+					    keyfileGroup.Visibility = ViewStates.Gone;
+					    break;
+				    case SftpModeSpinnerCustomKey:
+					    passwordBox.Visibility = ViewStates.Gone;
+					    publicKeyButton.Visibility = ViewStates.Gone;
+					    keyfileGroup.Visibility = ViewStates.Visible;
+					    break;
+			    }
 		    };
 
             if (!defaultPath.EndsWith(_schemeSeparator))
 		    {
-		        var fileStorage = new SftpStorage(activity.ApplicationContext);
                 SftpStorage.ConnectionInfo ci = fileStorage.SplitStringToConnectionInfo(defaultPath);
 		        dlgContents.FindViewById<EditText>(Resource.Id.sftp_host).Text = ci.Host;
 		        dlgContents.FindViewById<EditText>(Resource.Id.sftp_port).Text = ci.Port.ToString();
 		        dlgContents.FindViewById<EditText>(Resource.Id.sftp_user).Text = ci.Username;
 		        dlgContents.FindViewById<EditText>(Resource.Id.sftp_password).Text = ci.Password;
+				dlgContents.FindViewById<EditText>(Resource.Id.sftp_key_name).Text = ci.KeyName;
+				dlgContents.FindViewById<EditText>(Resource.Id.sftp_key_passphrase).Text = ci.KeyPassphrase;
 		        dlgContents.FindViewById<EditText>(Resource.Id.sftp_initial_dir).Text = ci.LocalPath;
 		        if (ci.ConnectTimeoutSec != SftpStorage.UnsetSftpConnectTimeout)
 		        {
 			        dlgContents.FindViewById<EditText>(Resource.Id.sftp_connect_timeout).Text = ci.ConnectTimeoutSec.ToString();
 		        }
-		        if (string.IsNullOrEmpty(ci.Password))
-		        {
-		            spinner.SetSelection(1);
-		        }
+
+				if (!string.IsNullOrEmpty(ci.Password))
+				{
+					authModeSpinner.SetSelection(SftpModeSpinnerPasswd);
+				} else if (!string.IsNullOrEmpty(ci.KeyName))
+				{
+					authModeSpinner.SetSelection(SftpModeSpinnerCustomKey);
+					keySpinner.SetSelection(ResolveKeySpinnerSelection(keyNamesAdapter, ci.KeyName));
+				} else
+				{
+					authModeSpinner.SetSelection(SftpModeSpinnerPubKey);
+				}
+
             }
 
 			builder.SetView(dlgContents);
-			builder.SetPositiveButton(Android.Resource.String.Ok,
-									  (sender, args) =>
-									  {
-										  string host = dlgContents.FindViewById<EditText>(Resource.Id.sftp_host).Text;
-										  string portText = dlgContents.FindViewById<EditText>(Resource.Id.sftp_port).Text;
-										  int port = SftpStorage.DefaultSftpPort;
-										  if (!string.IsNullOrEmpty(portText))
-											  int.TryParse(portText, out port);
-										  string user = dlgContents.FindViewById<EditText>(Resource.Id.sftp_user).Text;
-										  string password = dlgContents.FindViewById<EditText>(Resource.Id.sftp_password).Text;
-										  string initialPath = dlgContents.FindViewById<EditText>(Resource.Id.sftp_initial_dir).Text;
-									      if (string.IsNullOrEmpty(initialPath))
-									          initialPath = "/";
-									      string connectTimeoutText = dlgContents.FindViewById<EditText>(Resource.Id.sftp_connect_timeout).Text;
-									      int connectTimeout = SftpStorage.UnsetSftpConnectTimeout;
-									      if (!string.IsNullOrEmpty(connectTimeoutText)) {
-									          int.TryParse(connectTimeoutText, out connectTimeout);
-									      }
+            builder.SetPositiveButton(Android.Resource.String.Ok, (sender, args) => {
+				int idx = 0;
+                string host = dlgContents.FindViewById<EditText>(Resource.Id.sftp_host).Text;
+                string portText = dlgContents.FindViewById<EditText>(Resource.Id.sftp_port).Text;
+                int port = SftpStorage.DefaultSftpPort;
+                if (!string.IsNullOrEmpty(portText))
+                    int.TryParse(portText, out port);
+                string user = dlgContents.FindViewById<EditText>(Resource.Id.sftp_user).Text;
 
-                                          string sftpPath = new SftpStorage(activity.ApplicationContext)
-                                              .BuildFullPath(host, port, initialPath, user, password, connectTimeout);
-										  onStartBrowse(sftpPath);
-									  });
-			EventHandler<DialogClickEventArgs> evtH = new EventHandler<DialogClickEventArgs>((sender, e) => onCancel());
+                string password = null;
+                string keyName = null, keyPassphrase = null;
+                switch (dlgContents.FindViewById<Spinner>(Resource.Id.sftp_auth_mode_spinner).SelectedItemPosition)
+                {
+                    case SftpModeSpinnerPasswd:
+                        password = dlgContents.FindViewById<EditText>(Resource.Id.sftp_password).Text;
+                        break;
+                    case SftpModeSpinnerPubKey:
+                        break;
+                    case SftpModeSpinnerCustomKey:
+						keyName = ResolveSelectedKeyName(keyNamesAdapter, keySpinner.SelectedItemPosition);
+						keyPassphrase = dlgContents.FindViewById<EditText>(Resource.Id.sftp_key_passphrase).Text;
+                        break;
+                }
+
+                string initialPath = dlgContents.FindViewById<EditText>(Resource.Id.sftp_initial_dir).Text;
+                if (string.IsNullOrEmpty(initialPath))
+                    initialPath = "/";
+                string connectTimeoutText = dlgContents.FindViewById<EditText>(Resource.Id.sftp_connect_timeout).Text;
+                int connectTimeout = SftpStorage.UnsetSftpConnectTimeout;
+                if (!string.IsNullOrEmpty(connectTimeoutText))
+                {
+                    int.TryParse(connectTimeoutText, out connectTimeout);
+                }
+
+                string sftpPath = fileStorage.BuildFullPath(
+                    host, port, initialPath, user, password, connectTimeout, keyName, keyPassphrase);
+
+                onStartBrowse(sftpPath);
+            });
+            EventHandler<DialogClickEventArgs> evtH = new EventHandler<DialogClickEventArgs>((sender, e) => onCancel());
 
 			builder.SetNegativeButton(Android.Resource.String.Cancel, evtH);
 			builder.SetTitle(activity.GetString(Resource.String.enter_sftp_login_title));
@@ -139,9 +262,41 @@ namespace keepass2android
 
 			dialog.Show();
 #endif
-		}
+        }
 
-		private void ShowHttpDialog(Activity activity, Util.FileSelectedHandler onStartBrowse, Action onCancel, string defaultPath)
+#if !EXCLUDE_JAVAFILESTORAGE && !NoNet
+        private void UpdatePrivateKeyNames(ArrayAdapter dataView, SftpStorage storage, Context ctx)
+        {
+			dataView.Clear();
+			dataView.Add(ctx.GetString(Resource.String.private_key_create_new));
+			foreach (string keyName in storage.GetCustomKeyNames()) 
+				dataView.Add(keyName);
+        }
+
+        private int ResolveKeySpinnerSelection(ArrayAdapter dataView, string keyName)
+        {
+			int idx = -1;
+			for (int i = 0; i < dataView.Count; i++)
+			{
+				string itemName = dataView.GetItem(i).ToString();
+				if (string.Equals(keyName, itemName)) {
+					idx = i;
+					break;
+				}
+			}
+			return idx < 0 ? SftpKeySpinnerCreateNewIdx : idx;
+        }
+
+        private string ResolveSelectedKeyName(ArrayAdapter dataView, int selectedItem)
+        {
+            if (selectedItem != SftpKeySpinnerCreateNewIdx && selectedItem > 0 && selectedItem < dataView.Count)
+                return dataView.GetItem(selectedItem).ToString();
+            else
+                return null;
+        }
+#endif
+
+        private void ShowHttpDialog(Activity activity, Util.FileSelectedHandler onStartBrowse, Action onCancel, string defaultPath)
 		{
 #if !EXCLUDE_JAVAFILESTORAGE && !NoNet
 			AlertDialog.Builder builder = new AlertDialog.Builder(activity);

src/keepass2android/Resources/layout/sftpcredentials.xml

@@ -61,17 +61,80 @@
   </LinearLayout>
 		
 	<EditText
-            android:id="@+id/sftp_password"
+        android:id="@+id/sftp_password"
+        android:layout_width="fill_parent"
+        android:layout_height="wrap_content"
+        android:inputType="textPassword"
+        android:singleLine="true"
+        android:hint="@string/hint_pass"
+	    android:importantForAccessibility="no"/>
+
+    <Button
+        android:id="@+id/send_public_key_button"
+        android:layout_width="fill_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/send_public_key" />
+
+    <LinearLayout
+        android:id="@+id/sftp_keyfile_group"
+        android:orientation="vertical"
+        android:layout_width="fill_parent"
+        android:layout_height="wrap_content">
+	
+        <LinearLayout
+            android:orientation="horizontal"
+            android:layout_width="fill_parent"
+            android:layout_height="wrap_content">
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:text="@string/private_key_select" />
+            <Spinner
+                android:id="@+id/sftp_key_names"
+                android:layout_width="fill_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginLeft="3dp" />
+        </LinearLayout>
+
+        <LinearLayout
+            android:id="@+id/sftp_add_key_group"
+            android:orientation="vertical"
+            android:layout_width="fill_parent"
+            android:layout_height="wrap_content">
+            <EditText android:id="@+id/sftp_key_name"
+                android:layout_width="fill_parent"
+                android:layout_height="wrap_content"
+                android:hint="@string/hint_sftp_key_name" />
+		    <EditText
+                android:id="@+id/sftp_key_content"
+                android:layout_width="fill_parent"
+                android:layout_height="wrap_content"
+		        android:inputType="textMultiLine"
+                android:minLines="1"
+                android:maxLines="6"
+			    android:hint="@string/hint_sftp_key_content" />
+            <Button
+                android:id="@+id/sftp_save_key_button"
+                android:layout_width="fill_parent"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:text="@string/save_key" />
+         </LinearLayout>
+         <Button
+                android:id="@+id/sftp_delete_key_button"
+                android:layout_width="fill_parent"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:text="@string/delete_key" />
+        <EditText
+            android:id="@+id/sftp_key_passphrase"
             android:layout_width="fill_parent"
             android:layout_height="wrap_content"
-            android:inputType="textPassword"
             android:singleLine="true"
-            android:hint="@string/hint_pass"
-	          android:importantForAccessibility="no"/>
-  <Button  android:id="@+id/send_public_key_button"
-           android:layout_width="fill_parent"
-           android:layout_height="wrap_content"
-           android:text="@string/send_public_key" />
+		    android:inputType="textPassword"
+			android:hint="@string/hint_sftp_key_passphrase" />
+
+    </LinearLayout>
   
 		
 		<TextView android:id="@+id/initial_dir"
@@ -102,4 +165,4 @@
 			android:singleLine="true"
 			android:inputType="number" />
 
-</LinearLayout>
+</LinearLayout>

src/keepass2android/Resources/values/strings.xml

@@ -167,6 +167,7 @@
   <string name="hint_keyfile">key file</string>
   <string name="hint_length">length</string>
   <string name="hint_pass">password</string>
+  <string name="hint_keyfile_path">SSH private key path</string>
   <string name="hint_login_pass">Password</string>
   <string name="hint_title">name</string>
   <string name="hint_url">URL</string>
@@ -590,6 +591,19 @@
 	<string name="enter_sftp_login_title">Enter SFTP login data:</string>
   <string name="sftp_auth_mode">Authentication mode</string>
   <string name="send_public_key">Send public key...</string>
+  <string name="select_private_keyfile">Select private key...</string>
+	<string name="hint_sftp_key_name">New key name</string>
+	<string name="hint_sftp_key_content">New key content</string>
+	<string name="private_key_saved">Private key saved</string>
+	<string name="private_key_save_failed">FAILED to save private key: %1$s</string>
+	<string name="private_key_info">Enter key name and content to save</string>
+	<string name="private_key_delete">Deleted private key: %1$s</string>
+	<string name="private_key_delete_failed">FAILED to deleted private key: %1$s</string>
+	<string name="save_key">Save Private Key</string>
+	<string name="delete_key">Delete Private Key</string>
+	<string name="private_key_select">Selected private key</string>
+	<string name="private_key_create_new">[Add New...]</string>
+	<string name="hint_sftp_key_passphrase">Key passphrase (optional)</string>
 
   <string name="enter_ftp_login_title">Enter FTP login data:</string>
 
@@ -1322,7 +1336,8 @@ Initial public release
 	</string-array>
   <string-array name="sftp_auth_modes">
     <item>Password</item>
-    <item>Private/Public key</item>
+    <item>K2A Private/Public key</item>
+    <item>Custom Private key</item>
   </string-array>
 	<string-array name="AcceptAllServerCertificates_options">
 		<item>Ignore certificate validation failures</item>