modifications based on Akwizgran's comments

briar-android/src/org/briarproject/android/controller/PasswordControllerImpl.java

@@ -0,0 +1,54 @@
+package org.briarproject.android.controller;
+
+import android.app.Activity;
+
+import org.briarproject.android.controller.handler.ResultHandler;
+import org.briarproject.api.crypto.CryptoComponent;
+import org.briarproject.api.crypto.CryptoExecutor;
+import org.briarproject.api.crypto.SecretKey;
+import org.briarproject.util.StringUtils;
+
+import java.util.concurrent.Executor;
+
+import javax.inject.Inject;
+
+public class PasswordControllerImpl extends ConfigControllerImpl
+		implements PasswordController {
+
+	@Inject
+	@CryptoExecutor
+	protected Executor cryptoExecutor;
+	@Inject
+	protected CryptoComponent crypto;
+	@Inject
+	protected Activity activity;
+
+	@Inject
+	public PasswordControllerImpl() {
+
+	}
+
+	@Override
+	public void validatePassword(final String password,
+			final ResultHandler<Boolean> resultHandler) {
+		final byte[] encrypted = getEncryptedKey();
+		cryptoExecutor.execute(new Runnable() {
+			public void run() {
+				byte[] key = crypto.decryptWithPassword(encrypted, password);
+				if (key == null) {
+					resultHandler.onResult(false);
+				} else {
+					databaseConfig.setEncryptionKey(new SecretKey(key));
+					resultHandler.onResult(true);
+				}
+			}
+		});
+	}
+
+	private byte[] getEncryptedKey() {
+		String hex = getEncryptedDatabaseKey();
+		if (hex == null)
+			throw new IllegalStateException("Encrypted database key is null.");
+		return StringUtils.fromHexString(hex);
+	}
+}