[bouncy castle] AES CTR (128, 192, 256) with padding example

AES ECB Example

 

128, 192, 256의 의미는 키 길이의 bit수를 의미한다.

128 bit은 16 byte key 길이, 192 bit은 24 byte key 길이, 192 bit은 32 byte key 길이를 의미한다.

 

32 byte block을 암호화 /  복호화하는 예제

 

static byte[] aes_128bit_16byte = "ABCDEFGHIJKLMNOP".getBytes(StandardCharsets.UTF_8);
static byte[] aes_192bit_24byte = "ABCDEFGHIJKLMNOPQRSTUVWX".getBytes(StandardCharsets.UTF_8);
static byte[] aes_256bit_32byte = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef".getBytes(StandardCharsets.UTF_8);

public byte[] aesCtrPadEncrypt(byte[] key, byte[] text, byte[] iv) throws InvalidCipherTextException {
    if (iv == null) {
        iv = new byte[16];
    }
    // create AES cipher
    BlockCipher engine = new AESEngine();
    // Padding cipher (adjust input data length to des block size)
    BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new SICBlockCipher(engine));
    // set key
    cipher.init(true, new ParametersWithIV(new KeyParameter(key), iv));

    int outputSize = cipher.getOutputSize(text.length);
    byte[] outBuff = new byte[outputSize];
    int offset = cipher.processBytes(text, 0, text.length, outBuff, 0);
    cipher.doFinal(outBuff, offset);

    return outBuff;
}

public byte[] aesCtrPadDecrypt(byte[] key, byte[] text, byte[] iv) throws InvalidCipherTextException {
    if (iv == null) {
        iv = new byte[16];
    }
    // create AES cipher
    BlockCipher engine = new AESEngine();
    // Padding cipher (adjust input data length to des block size)
    BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new SICBlockCipher(engine));
    // set key
    cipher.init(false, new ParametersWithIV(new KeyParameter(key), iv));

    int outputSize = cipher.getOutputSize(text.length);
    byte[] outBuff = new byte[outputSize];
    int offset = cipher.processBytes(text, 0, text.length, outBuff, 0);
    int ret = cipher.doFinal(outBuff, offset);

    return Arrays.copyOf(outBuff, offset+ret);
}

void aesCtrPadExample() throws InvalidCipherTextException {
    byte[] text = "pass".getBytes(StandardCharsets.UTF_8);
    byte[] ret;

    ret = aesCtrPadEncrypt(aes_128bit_16byte, text, null);
    print(ret);
    ret = aesCtrPadDecrypt(aes_128bit_16byte, ret, null);
    System.out.println(new String(ret, StandardCharsets.UTF_8));

    ret = aesCtrPadEncrypt(aes_192bit_24byte, text, null);
    print(ret);
    ret = aesCtrPadDecrypt(aes_192bit_24byte, ret, null);
    System.out.println(new String(ret, StandardCharsets.UTF_8));

    ret = aesCtrPadEncrypt(aes_256bit_32byte, text, null);
    print(ret);
    ret = aesCtrPadDecrypt(aes_256bit_32byte, ret, null);
    System.out.println(new String(ret, StandardCharsets.UTF_8));
}

 

 

결과: 각 키 길이별 첫번째 라인은 암호화한 결과, 두번째 라인은 복호화한 결과

// 128 bit 16 byte 
F5:14:A2:9B:9F:9D:75:D1:A4:69:12:E2:24:F4:91:71
pass

// 192 bit 24 byte
39:94:A7:74:AA:25:13:12:4F:31:D2:7E:0F:2E:35:E6
pass

// 256 bit 32 byte
F0:C4:1A:4E:53:0F:9C:90:13:76:CF:8A:9A:C8:F2:89
pass

 

 

코드위치

https://github.com/coolbong/BouncyCastleExample/blob/master/src/main/java/io/github/coolbong/Aes.java