AES Java Implementation

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Description

The following is a simple Java example of AES encryption and decryption, compatible with the LSL AES Engine by Haravikk Mistral.

Required Classes

Base64Coder

<java>package lslAESCrypto;

/** 

* A Base64 Encoder/Decoder.

*

* This class is used to encode and decode data in Base64 format as described in * RFC 1521. * 

*/

public class Base64Coder { /** Mapping table from 6-bits to Base64 characters. */ private static char[] BITS_TO_BASE64_CHAR = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };

/** Mapping table from Base64 characters to 6-bits. */ private static byte[] BASE64_CHAR_TO_BITS = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, };

/** * Decodes a byte array from Base64 format. No blanks or line breaks are * allowed within the Base64 encoded data. * * @param in * a character array containing the Base64 encoded data. * @return An array containing the decoded data bytes. * @throws IllegalArgumentException * if the input is not valid Base64 encoded data. */ public static byte[] decode(final char[] in) throws IllegalArgumentException { int len = in.length; if (len % 4 != 0) throw new IllegalArgumentException( "Length of Base64 encoded input string is not a multiple of 4.");

// Ignore trailing equals while (len > 0 && in[len - 1] == '=') --len;

final byte[] bytes = new byte[(len * 3) / 4]; int o = 0;

for (int i = 0; i < len;) { try { final char c0 = in[i++]; final char c1 = in[i++]; final char c2 = (i < len) ? in[i++] : 'A'; final char c3 = (i < len) ? in[i++] : 'A';

if (c0 > 127 || c1 > 127 || c2 > 127 || c3 > 127) throw new IllegalArgumentException( "Invalid base64 character");

final byte b0 = Base64Coder.BASE64_CHAR_TO_BITS[c0]; final byte b1 = Base64Coder.BASE64_CHAR_TO_BITS[c1]; final byte b2 = Base64Coder.BASE64_CHAR_TO_BITS[c2]; final byte b3 = Base64Coder.BASE64_CHAR_TO_BITS[c3];

if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0) throw new IllegalArgumentException( "Invalid base64 character");

bytes[o++] = (byte) ((b0 << 2) | (b1 >>> 4)); if (o < bytes.length) { bytes[o++] = (byte) (((b1 & 0xF) << 4) | (b2 >>> 2)); if (o < bytes.length) bytes[o++] = (byte) (((b2 & 0x3) << 6) | b3); } } catch (final ArrayIndexOutOfBoundsException e) { throw new IllegalArgumentException("Invalid base64 character"); } }

return bytes; }

/** * Decodes a byte array from Base64 format. * * @param s * a Base64 String to be decoded. * @return An array containing the decoded data bytes. * @throws IllegalArgumentException * if the input is not valid Base64 encoded data. */ public static byte[] decode(final String s) { return Base64Coder.decode(s.toCharArray()); }

/** * Decodes a string from Base64 format. * * @param s * a Base64 String to be decoded. * @return A String containing the decoded data. * @throws IllegalArgumentException * if the input is not valid Base64 encoded data. */ public static String decodeString(final String s) { return new String(Base64Coder.decode(s)); }

/** * Encodes a byte array into Base64 format. No blanks or line breaks are * inserted. * * @param in * an array containing the data bytes to be encoded. * @return A character array with the Base64 encoded data. */ public static char[] encode(final byte[] in) { return Base64Coder.encode(in, 0, in.length); }

/** * Encodes a byte array into Base64 format. No blanks or line breaks are * inserted. * * @param in * an array containing the data bytes to be encoded. * @param offset * the offset into the array at which to begin reading. * @param bits * number of bits to process from in. * @return A character array with the Base64 encoded data. */ public static char[] encode( final byte[] in, final int offset, final int bits) { int length = bits / 8; if ((length * 8) < bits) ++length;

final char[] chars = new char[((length + 2) / 3) * 4]; final int out = ((length * 4) + 2) / 3;

int mask = ~(-1 << (8 - (bits % 8))) | ~(-1 << (bits % 8)); if (mask == 0) mask = 0xFF;

int o = 0; final int end = length + offset; for (int i = offset; i < end;) { final int b0 = ((i + 1) == end) ? in[i++] & mask : in[i++] & 0xFF; final int b1 = (i < length) ? (((i + 1) == end) ? in[i++] & mask : in[i++] & 0xFF) : 0; final int b2 = (i < length) ? (((i + 1) == end) ? in[i++] & mask : in[i++] & 0xFF) : 0;

final int i0 = (b0 >>> 2); final int i1 = (((b0 & 0x3) << 4) | (b1 >>> 4)); final int i2 = (((b1 & 0xF) << 2) | (b2 >>> 6)); final int i3 = b2 & 0x3F;

chars[o++] = Base64Coder.BITS_TO_BASE64_CHAR[i0]; chars[o++] = Base64Coder.BITS_TO_BASE64_CHAR[i1]; chars[o] = (o < out) ? Base64Coder.BITS_TO_BASE64_CHAR[i2] : '='; ++o; chars[o] = (o < out) ? Base64Coder.BITS_TO_BASE64_CHAR[i3] : '='; ++o; }

return chars; }

/** * Produces a base64 string from the provided byte-array. * * @param bytes * the byte-array to read-from. * @return the base64 encoded string produced. */ public static String encodeString(final byte[] bytes) { return Base64Coder.encodeString(bytes, 0, bytes.length); }

/** * Produces a base64 string from the provided byte-array slice. * * @param bytes * the byte-array to read-from. * @param offset * the offset into the array at which to begin reading. * @param bits * number of bits to process from bytes. * @return the base64 encoded string produced. */ public static String encodeString( final byte[] bytes, final int offset, final int bits) { return new String(Base64Coder.encode(bytes, offset, bits)); }

/** * Encodes a string into Base64 format. No blanks or line breaks are * inserted. * * @param s * a String to be encoded. * @return A String with the Base64 encoded data. */ public static String encodeString(final String s) { return new String(Base64Coder.encode(s.getBytes())); }

/** Dummy constructor. */ private Base64Coder() { /* Blocking constructor */}

}</java>

HexCoder

<java>package lslAESCrypto; /** 

* The following is a simple set of static methods for converting from hex to
* bytes and vice-versa
* 
* @author Haravikk Mistral
* @date Sep 15, 2008, 3:26:42 PM
* @version 1.0
*/

public class HexCoder { /** * Quick converts bytes to hex-characters * * @param bytes * the byte-array to convert * @return the hex-representation */ public static String bytesToHex(final byte[] bytes) { final StringBuffer s = new StringBuffer(bytes.length * 2); for (int i = 0; i < bytes.length; ++i) { s.append(Character.forDigit((bytes[i] >> 4) & 0xF, 16)); s.append(Character.forDigit(bytes[i] & 0xF, 16)); } return s.toString(); }

/** * Quickly converts hex-characters to bytes * * @param s * the hex-string * @return the bytes represented */ public static byte[] hexToBytes(final String s) { final byte[] bytes = new byte[s.length() / 2]; for (int i = 0; i < bytes.length; ++i) bytes[i] = (byte) Integer.parseInt( s.substring(2 * i, (2 * i) + 2), 16); return bytes; } } </java>

Class

<java>package lslAESCrypto;

import java.security.InvalidAlgorithmParameterException; import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.util.Random;

import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeException; import javax.crypto.NoSuchPaddingException; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.SecretKeySpec;

/**

*

* This is a class designed to process AES messages sent from the LSL * implementation of AES which can be found here:
* <a * href="https://wiki.secondlife.com/wiki/AES_LSL_Implementation">https://wiki * .secondlife.com/wiki/AES_LSL_Implementation</a> *

*

* This Java class will be updated to support the same modes of operation as the * LSL implementation. It currently assumes that keys and input-vectors are * processed as hex-strings, and that text is received as plain-text, while * ciphertext will be handled as base64 strings. * 

* 
* @author Haravikk
* @date Sep 15, 2008, 4:18:48 PM
* @version 1.0
*/

public class LSLAESCrypto { /** Our currently set block-cipher mode */ protected LSLAESCryptoMode mode = LSLAESCryptoMode.CBC; /** Used to detect when a new {@link Cipher} Is needed. */ protected boolean modeChanged = false;

/** Our currently set padding mode */ protected LSLAESCryptoPad pad = LSLAESCryptoPad.NONE; /** Our currently set pad-size */ protected int padSize = 512;

/** The currently loaded key */ protected SecretKeySpec keySpec = null; /** The currently loaded input-vector */ protected IvParameterSpec ivSpec = null;

/** The currently active cipher */ protected Cipher cipher = null;

/** A random class for secure random operations. */ protected Random random = new SecureRandom();

/** * Creates an instance of an LSL compatible AES handler. * * @param mode * the cipher-block mode of operation * @param pad * the padding scheme to use * @param padSize * the block-size to use when padding. Must be a non-zero, * positive value that is a multiple of 128. * @param hexKey * the key to start with (represented as hexadecimal string) * @param hexIV * the input vector to start with (represented as hexadecimal * string) * @throws NoSuchAlgorithmException * if the AES algorithm is not supported by the current JVM * @throws NoSuchPaddingException * if the padding scheme chosen is not supported by the current * JVM */ public LSLAESCrypto( final LSLAESCryptoMode mode, final LSLAESCryptoPad pad, final int padSize, final String hexKey, final String hexIV) throws NoSuchAlgorithmException, NoSuchPaddingException { this.init(mode, pad, padSize, hexKey, hexIV); }

/** * Decrypts a base64 ciphertext into plain-text * * @param base64ciphertext * the ciphertext to decrypt * @return the plain-text that was originally encrypted * @throws InvalidKeyException * if the currently loaded key is not valid * @throws InvalidAlgorithmParameterException * if the AES algorithm is not supported by the current JVM * @throws IllegalBlockSizeException * if the ciphertext is somehow unreadable (bad base64 * conversion) * @throws BadPaddingException * if the chosen mode of operation requires padded data */ public String decrypt(final String base64ciphertext) throws InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException { if (this.modeChanged) try { this.createCipher(); } catch (final Exception e) { /* Do nothing */}

this.cipher.init(Cipher.DECRYPT_MODE, this.keySpec, this.ivSpec); return new String(this.cipher.doFinal(Base64Coder .decode(base64ciphertext))); }

/** * Encrypts plain-text into a base64 string * * @param text * the plain-text to encrypt * @return the base64 ciphertext produced * @throws IllegalBlockSizeException * if the plain text is somehow invalid * @throws BadPaddingException * if the chosen mode of operation requires padded data * @throws InvalidKeyException * if the currently loaded key is invalid * @throws InvalidAlgorithmParameterException * if the AES algorithm is not supported by the current JVM */ public String encrypt(final String text) throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException { if (this.modeChanged) try { this.createCipher(); } catch (final Exception e) { /* Do nothing */}

this.cipher.init(Cipher.ENCRYPT_MODE, this.keySpec, this.ivSpec);

byte[] data = text.getBytes(); int bits = data.length * 8;

/* Apply padding */ LSLAESCryptoPad padding = this.pad; if (padding == LSLAESCryptoPad.NONE) { if (this.mode == LSLAESCryptoMode.CFB) { return Base64Coder .encodeString(this.cipher.doFinal(data), 0, bits); } padding = LSLAESCryptoPad.RBT; }

int blockSize = this.padSize; if (padding == LSLAESCryptoPad.RBT) blockSize = 128;

final int blocks = bits / blockSize; int extra = bits % blockSize;

if (padding == LSLAESCryptoPad.RBT) { if (extra > 0) { /* * This scheme takes the last encrypted block, encrypts it * again, and XORs it with any leftover data, maintaining * data-length. If input is less than a block in size, then the * current input-vector is used. */ int bytes = extra / 8; if ((bytes * 8) < extra) ++bytes;

// Grab leftover bytes final byte[] t = new byte[bytes]; if (bytes > 0) System.arraycopy(data, data.length - bytes, t, 0, bytes);

// Encrypt all other data. byte[] lb; if (blocks < 1) { // If not enough for a block, double-encrypt IV. data = new byte[0]; lb = this.cipher.doFinal(this.cipher.doFinal(this.ivSpec .getIV())); } else { // If there are blocks, then double-encrypt final one. data = this.cipher.doFinal(data, 0, data.length - bytes); lb = this.cipher.doFinal(data, data.length - 16, 16); }

// XOR lb with t. for (int i = 0; i < t.length; ++i) t[i] ^= lb[i];

lb = new byte[data.length + t.length]; System.arraycopy(data, 0, lb, 0, data.length); System.arraycopy(t, 0, lb, data.length, t.length);

return Base64Coder.encodeString(lb); } return Base64Coder.encodeString(this.cipher.doFinal(data), 0, bits); }

// Padding schemes that add bytes until block-boundary is reached. extra = blockSize - extra;

if (padding == LSLAESCryptoPad.NULLS_SAFE) { ++bits; final int bytes = bits / 8; final int bit = bytes % 8;

if (bytes < data.length) data[bytes] |= (1 << (8 - bit)); else { final byte[] t = new byte[data.length + 1]; System.arraycopy(data, 0, t, 0, data.length); t[data.length] = (byte) 0x80; data = t; }

if ((--extra) < 0) extra += blockSize; padding = LSLAESCryptoPad.NULLS; }

int bytes = extra / 8; if (bytes <= 0) { if (padding == LSLAESCryptoPad.NULLS) return Base64Coder.encodeString( this.cipher.doFinal(data), 0, bits);

bytes = blockSize / 8; extra += blockSize; }

bits += extra; final byte[] t = new byte[data.length + bytes]; int i = data.length; System.arraycopy(data, 0, t, 0, data.length); data = t;

for (; i < data.length; ++i) { byte b = 0; if ((i >= (data.length - 4)) && (padding != LSLAESCryptoPad.NULLS)) b = (byte) bytes; else if (padding == LSLAESCryptoPad.RANDOM) b = (byte) this.random.nextInt(256);

data[i] = b; }

return Base64Coder.encodeString(this.cipher.doFinal(data), 0, bits); }

/** * Initialises this AES instance with a mode, pad, key, and input vector in * a single operation * * @param mode * the cipher-block mode of operation * @param pad * the padding scheme to use * @param padSize * the block-size to use when padding. Must be a non-zero, * positive value that is a multiple of 128. * @param hexKey * the key to use as a hexadecimal string * @param hexIV * the input-vector to use as a hexadecimal string * @throws NoSuchAlgorithmException * if the AES algorithm is not supported by the current JVM * @throws NoSuchPaddingException * if the padding method is not supported by the current JVM */ public void init( final LSLAESCryptoMode mode, final LSLAESCryptoPad pad, final int padSize, final String hexKey, final String hexIV) throws NoSuchAlgorithmException, NoSuchPaddingException { if ((mode == null) || (pad == null) || (hexKey == null) || (hexIV == null)) throw new IllegalArgumentException("No arguments may be null");

this.setMode(mode); this.setPad(pad, padSize); this.setKey(hexKey); this.setInputVector(hexIV);

this.random.nextInt();

this.createCipher(); }

/** * Sets the input-vector for this engine to use * * @param hexIV * a hexadecimal input-vector to use */ public void setInputVector(final String hexIV) { if (hexIV == null) throw new IllegalArgumentException("Input-vector may not be null!");

this.ivSpec = new IvParameterSpec(HexCoder.hexToBytes(hexIV)); }

/** * Sets the key for this engine to use * * @param hexKey * a hexadecimal key to use */ public void setKey(final String hexKey) { if (hexKey == null) throw new IllegalArgumentException("Key may not be null!");

this.keySpec = new SecretKeySpec(HexCoder.hexToBytes(hexKey), "AES"); }

/** * Sets the mode of this implementation * * @param mode * the mode to set */ public void setMode(final LSLAESCryptoMode mode) { if (mode == null) throw new IllegalArgumentException("Mode may not be null!");

this.mode = mode; this.modeChanged = true; }

/** * Sets the padding scheme of this implementation * * @param pad * the padding scheme to use */ public void setPad(final LSLAESCryptoPad pad) { this.setPad(pad, this.padSize); }

/** * Sets the padding scheme of this implementation * * @param pad * the padding scheme to use * @param padSize * the block-size to use when padding. Must be a non-zero, * positive value that is a multiple of 128. */ public void setPad(final LSLAESCryptoPad pad, final int padSize) { if (pad == null) throw new IllegalArgumentException("Pad may not be null!"); if ((padSize <= 0) || ((padSize % 128) > 0)) throw new IllegalArgumentException( "Pad size may not be less than zero, and must be a multiple of 128");

this.pad = pad; this.padSize = padSize; }

/** * Creates a new cipher instance for processing * * @throws NoSuchPaddingException * if the padding scheme set is invalid * @throws NoSuchAlgorithmException * if AES is not supported by this JVM */ protected void createCipher() throws NoSuchAlgorithmException, NoSuchPaddingException { this.cipher = Cipher.getInstance("AES/" + this.mode + "/NoPadding"); }

/** Defines modes of operation combatible with LSL */ public enum LSLAESCryptoMode { /** Cipher-Block-Chaining mode */ CBC, /** Cipher FeedBack mode */ CFB; }

/** Defines padding schemes compatible with LSL */ public enum LSLAESCryptoPad { /** Performs no padding, will switch to RBT if mode is CBC. */ NONE, /** * Enables CFB mode temporarily for the final complete block, and * combines with data. This preserves data-length. */ RBT, /** * Adds null-bytes to the end of the data until it is of correct-size. * This is an padding scheme (may result in loss of null-bytes from * original data). */ NULLS, /** * Same as NULLS, except that it first appends a single '1' bit to the * data before padding. */ NULLS_SAFE, /** * Appends null-bytes to the data until one word from block-size, final * word is then populated with bytes describing the number of padding * bytes added. */ ZEROES, /** * Same as ZEROES, except that random-bytes are used in place of * null-bytes. */ RANDOM; } }</java>

Examples

Encryption

<java>import lslAESCrypto.LSLAESCrypto; import lslAESCrypto.LSLAESCrypto.LSLAESCryptoMode; import lslAESCrypto.LSLAESCrypto.LSLAESCryptoPad;

/** */ public class ExampleEncrypt { /** * @param args * @throws Exception */ public static void main(final String[] args) throws Exception { final String myKey = "1234567890ABCDEF0123456789ABCDEF"; final String myIV = "89ABCDEF0123456789ABCDEF01234567"; final String myMsg = "Hello world! I am a lovely message waiting to be encrypted!";

final LSLAESCrypto aes = new LSLAESCrypto( LSLAESCryptoMode.CFB, LSLAESCryptoPad.NoPadding, myKey, myIV); System.out.println(aes.encrypt(myMsg)); } }</java>

Decryption

<java>import lslAESCrypto.LSLAESCrypto; import lslAESCrypto.LSLAESCrypto.LSLAESCryptoMode; import lslAESCrypto.LSLAESCrypto.LSLAESCryptoPad;

/** */ public class ExampleDecrypt { /** * @param args * @throws Exception */ public static void main(final String[] args) throws Exception { final String myKey = "1234567890ABCDEF0123456789ABCDEF"; final String myIV = "89ABCDEF0123456789ABCDEF01234567"; final String myMsg = "Mdn6jGTwRPMOKTYTTdDKGm9KScz26LIz96KVOGAeMw3hpwByPfa07PDRHxRW4TIh5dmu5LlhKpTQChi=";

final LSLAESCrypto aes = new LSLAESCrypto( LSLAESCryptoMode.CFB, LSLAESCryptoPad.NoPadding, myKey, myIV); System.out.println(aes.decrypt(myMsg)); } }</java>

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