Java AES 256 encryption

Question

I have the below java code to encrypt a string which uses a 64 character key. My question is will this be a AES-256 encryption?

String keyString = "C0BAE23DF8B51807B3E17D21925FADF273A70181E1D81B8EDE6C76A5C1F1716E";
byte[] keyValue = hexStringToByte(keyString);
Key key = new SecretKeySpec(keyValue, "AES");
Cipher c1 = Cipher.getInstance("AES");
c1.init(Cipher.ENCRYPT_MODE, key);

String data = "Some data to encrypt";
byte[] encVal = c1.doFinal(data.getBytes());
String encryptedValue = Base64.encodeBase64String(encVal);


/* Copied the below code from another post in stackexchange */
public static byte[] hexStringToByte(String hexstr) 
{
  byte[] retVal = new BigInteger(hexstr, 16).toByteArray();
  if (retVal[0] == 0) 
  {
    byte[] newArray = new byte[retVal.length - 1];
    System.arraycopy(retVal, 1, newArray, 0, newArray.length);
    return newArray;
  }
  return retVal;
}

The following is the code after incorporating suggestions from divanov and laz.

String keyString = "C0BAE23DF8B51807B3E17D21925FADF273A70181E1D81B8EDE6C76A5C1F1716E";
byte[] keyValue = DatatypeConverter.parseHexBinary(keyString);
Key key = new SecretKeySpec(keyValue, "AES");
Cipher c1 = Cipher.getInstance("AES");
c1.init(Cipher.ENCRYPT_MODE, key);

String data = "Some data to encrypt";
byte[] encVal = c1.doFinal(data.getBytes());
String encryptedValue = Base64.encodeBase64String(encVal);

possible duplicate of [Java 256-bit AES Password-Based Encryption](http://stackoverflow.com/questions/992019/java-256-bit-aes-password-based-encryption) — Elliott Frisch, Feb 03 '14 at 03:57
Where is that post that performs the incorrect hex decoding? I desperately need to downvote it. — Maarten Bodewes, Feb 03 '14 at 20:11

divanov · Accepted Answer · 2014-02-03T07:36:22.137

3

Yes, it will as 64 characters are 32 bytes and 256 bits and any sequence of 256 bits can be used as an AES-256 key.

I suggest you to use DatatypeConverter.parseHexBinary (or similar utility from library of your choice) to convert hexadecimal strings into byte arrays.

edited Feb 03 '14 at 07:36

answered Feb 03 '14 at 05:24

divanov

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Really? Did you see `byte[] new = new byte[retVal.length - 1];`? – Elliott Frisch Feb 03 '14 at 05:31
This is a clumsy attempt to deal with sign byte appended by BigInteger. – divanov Feb 03 '14 at 05:37
1

There is `DatatypeConverter` that is part of the main Java API for decoding the hex string as well: http://docs.oracle.com/javase/7/docs/api/javax/xml/bind/DatatypeConverter.html#parseHexBinary%28java.lang.String%29 – laz Feb 03 '14 at 06:35

Java AES 256 encryption

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