z28cLRyP

1SecretKey aesKey = new SecretKeySpec(new byte[256 / Byte.SIZE], "AES");
2byte[] pt = "owlstead".getBytes(StandardCharsets.US_ASCII);
3
4{
5    // === CBC mode requires an IV of the same size as the block size
6    Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
7    // changing the IV size will result in an exception
8    byte[] ivBytes = new byte[c.getBlockSize()];
9    IvParameterSpec iv = new IvParameterSpec(ivBytes);
10    c.init(Cipher.ENCRYPT_MODE, aesKey, iv);
11    byte[] ct = c.doFinal(pt);
12    System.out.println(Hex.toHexString(ct));
13}
14
15{
16    // === CTR mode actually requires a complete IV in Java
17    // Java (or actually, the SUN provider) requires a 128 bit IV instead of just a nonce
18    Cipher c = Cipher.getInstance("AES/CTR/NoPadding");
19    // changing the IV size will result in an exception
20    byte[] ivBytes = new byte[c.getBlockSize()];
21    IvParameterSpec iv = new IvParameterSpec(ivBytes);
22    c.init(Cipher.ENCRYPT_MODE, aesKey, iv);
23    byte[] ct = c.doFinal(pt);
24    System.out.println(Hex.toHexString(ct));
25}
26
27{
28    // === GCM mode can do it!
29    Cipher c = Cipher.getInstance("AES/GCM/NoPadding");
30    byte[] ivBytes = new byte[256 / Byte.SIZE];
31    GCMParameterSpec gcmSpecWithIV = new GCMParameterSpec(128, ivBytes);
32    c.init(Cipher.ENCRYPT_MODE, aesKey, gcmSpecWithIV);
33    byte[] ct = c.doFinal(pt);
34    System.out.println(Hex.toHexString(ct));
35}
36
37{
38    // ===  java.security.InvalidAlgorithmParameterException: ECB mode cannot use IV
39    Cipher c = Cipher.getInstance("AES/ECB/PKCS5Padding");
40    byte[] ivBytes = new byte[c.getBlockSize()];
41    IvParameterSpec iv = new IvParameterSpec(ivBytes);
42    c.init(Cipher.ENCRYPT_MODE, aesKey, iv);
43    byte[] ct = c.doFinal(pt);
44    System.out.println(Hex.toHexString(ct));
45}