Java aes key to 32byte string representation

Question

How can this be done? I want to take the resulting aes secretkey and turn it into the plaintext 16byte representation

        public SecretKey generateAesKey() throws NoSuchAlgorithmException{
                KeyGenerator keygen;
                keygen = KeyGenerator.getInstance("AES");
                keygen.init(128);
                SecretKey aesKey = keygen.generateKey();
                return aesKey;
        }

Im using this to generate the key (Pretty sure the key would be 32 bytes, unless I'm thinking of 256bit key?)

Flowryn · Answer 1 · 2015-07-24T02:39:42.387

SecretKey class has a method .getEncoded() which will return your key.

You can obtain your string representation in hexadecimal (for example) using the following method:

private static String bytesToHexRepresentation(byte[] bytes) {
    StringBuilder sb = new StringBuilder();
    for (byte b : bytes) {
        sb.append(String.format("%02X ", b));
    }
    return sb.toString();
}

therefore you can do:

SecretKey myKey = generateAesKey();
byte[] encodedBytes = myKey.getEncoded();
String s = bytesToHexRepresentation(encodedBytes);
System.out.printf(s);

To print your key in a nice hexadecimal representation.

As for your second question:

for 128 bits the key is 16 bytes (your current case)
for 192 bits the key is 24 bytes
for 256 bits the key is 32 bytes

Java aes key to 32byte string representation

1 Answers1