CODEWITHSUNDEEP
androidencryptionaes
newbie dev
newbie dev

Reputation: 171

Encryption/Decryption in Android

I have done encryption in android with a static password i.e. "encrypt". The encryption works fine and encrypts the data. But when i try to decrypt the encrypted text it does not show. The code to decrypt is as follow.

public String decrypt(String msg, String inputPassword) throws Exception{
    SecretKeySpec key= generateKey(inputPassword);
    Cipher c = Cipher.getInstance(AES);
    c.init(Cipher.DECRYPT_MODE, key);
    byte[] decodedValue= Base64.decode(msg, Base64.DEFAULT);

    /*If this line is present the encrypted message is not seen*/
    byte[] decValue = c.doFinal(Base64.decode(decodedValue, 
Base64.DEFAULT));
    String decryptedValue = new String(decodedValue);
    String decryptedValue = new String(decValue, StandardCharsets.UTF_8);
    return decryptedValue;
}

When the code (below the comment) is enabled. The message is not displayed. But when the line is commented. This is shown in the message box

After the code is commented.

This is the encrypt and key generate methods.

public String encrypt(String message, String inputPassword) throws Exception{
    SecretKeySpec key = generateKey(inputPassword);
    Cipher c = Cipher.getInstance(AES);
    c.init(c.ENCRYPT_MODE, key);
    byte[] encVal = c.doFinal(message.getBytes());
    String encryptedValue = Base64.encodeToString(encVal, Base64.DEFAULT);
    return encryptedValue;
}

//For generating key for encryption
public SecretKeySpec generateKey(String inputPassword) throws  Exception{
    final MessageDigest digest = MessageDigest.getInstance("SHA-256");
    byte[] bytes = inputPassword.getBytes("UTF-8");
    digest.update(bytes, 0, bytes.length);
    byte[] key = digest.digest();
    SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
    return secretKeySpec;
}

The log is follow enter image description here

Also the API level is not maintained... I don't know where to setup this as well. enter image description here

Upvotes: 0

Views: 636

Answers (1)

Bach Vu
Bach Vu

Reputation: 2348

Could you try changing this

String decryptedValue = new String(decodedValue)

to this

String decryptedValue = new String(decodedValue, StandardCharsets.UTF_8)

And for your error, try changing to this

c.doFinal(Base64.decode(decodedValue, Base64.DEFAULT))

Upvotes: 1

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