Hello, I was a bit confused about the use of UTF-8 for converting a number to bytes, but when I looked more closely, it is even more confusing why a decimal number is used and converted here at all. If I understand it right the format of the bytes and the length is unconstrained? I would recommend to use 7 byte array with binary content. But even using Hex or radix=36 strings would reduce the byte[] size without losing entropy. private Nonce createNewNonce(NonceHolder previousNonce) { byte[] prefix = new byte[8]; random.nextBytes(prefix); long timeStamp = System.currentTimeMillis(); byte[] now = Long.toString(timeStamp).getBytes(UTF_8); String nonce = createNonce(prefix, now); -> byte[] now = Long.toString(timeStamp,36).getBytes(StandardCharsets.ISO_8859_1) This makes the byte array shorter and the conversion slightly faster, here are the timing for the various byte encoders on different string formats (base-10,16,32,36) (8threads): Benchmark (number) Mode Samples Score Score error Units n.e.t.l.MyBenchmark.testGetBytesASCII 1401994160926 thrpt 80 4932,143 41,752 ops/ms n.e.t.l.MyBenchmark.testGetBytesASCII 1466d5d2b1e thrpt 80 5270,165 64,343 ops/ms n.e.t.l.MyBenchmark.testGetBytesASCII 18pmlqaou thrpt 80 5521,322 119,856 ops/ms n.e.t.l.MyBenchmark.testGetBytesASCII hw2f4hzy thrpt 80 5929,315 62,562 ops/ms n.e.t.l.MyBenchmark.testGetBytesBase 1401994160926 thrpt 80 154669,919 3845,919 ops/ms n.e.t.l.MyBenchmark.testGetBytesBase 1466d5d2b1e thrpt 80 155290,761 1678,557 ops/ms n.e.t.l.MyBenchmark.testGetBytesBase 18pmlqaou thrpt 80 152989,174 5648,101 ops/ms n.e.t.l.MyBenchmark.testGetBytesBase hw2f4hzy thrpt 80 154360,497 3022,226 ops/ms n.e.t.l.MyBenchmark.testGetBytesDefault 1401994160926 thrpt 80 2319,440 47,902 ops/ms n.e.t.l.MyBenchmark.testGetBytesDefault 1466d5d2b1e thrpt 80 2648,794 29,700 ops/ms n.e.t.l.MyBenchmark.testGetBytesDefault 18pmlqaou thrpt 80 3098,998 36,169 ops/ms n.e.t.l.MyBenchmark.testGetBytesDefault hw2f4hzy thrpt 80 3364,678 33,274 ops/ms n.e.t.l.MyBenchmark.testGetBytesLATIN1 1401994160926 thrpt 80 5202,078 189,594 ops/ms n.e.t.l.MyBenchmark.testGetBytesLATIN1 1466d5d2b1e thrpt 80 6166,294 64,541 ops/ms n.e.t.l.MyBenchmark.testGetBytesLATIN1 18pmlqaou thrpt 80 6677,003 130,301 ops/ms n.e.t.l.MyBenchmark.testGetBytesLATIN1 hw2f4hzy thrpt 80 6293,458 331,745 ops/ms n.e.t.l.MyBenchmark.testGetBytesLower 1401994160926 thrpt 80 10332,605 114,527 ops/ms n.e.t.l.MyBenchmark.testGetBytesLower 1466d5d2b1e thrpt 80 10173,196 120,769 ops/ms n.e.t.l.MyBenchmark.testGetBytesLower 18pmlqaou thrpt 80 10392,109 150,898 ops/ms n.e.t.l.MyBenchmark.testGetBytesLower hw2f4hzy thrpt 80 10584,135 140,522 ops/ms n.e.t.l.MyBenchmark.testGetBytesUTF8 1401994160926 thrpt 80 4998,594 115,126 ops/ms n.e.t.l.MyBenchmark.testGetBytesUTF8 1466d5d2b1e thrpt 80 5184,154 72,303 ops/ms n.e.t.l.MyBenchmark.testGetBytesUTF8 18pmlqaou thrpt 80 5395,096 98,476 ops/ms n.e.t.l.MyBenchmark.testGetBytesUTF8 hw2f4hzy thrpt 80 5212,183 142,887 ops/ms (Lower=loop over char array and use lower byte) However I wonder if longToLower7Bytes(now) would be even more efficient? Both changes needs to be reflected in verifyUnknownNonce() as well. This would benefit from a byte nonce as well, as you could for example not anymore trigger NumberFormatException with invalid nonces. Want me to provide a binary version? How would the compatibility be handled? (Using base10+ASCII is compatible, all other changes not). The native version minimizes the GC load as well: Benchmark (number) Mode Samples Score Score error Units n.e.t.l.MyBenchmark.testGetBytesNative 1401994160926 thrpt 80 31669,314 260,181 ops/ms n.e.t.l.MyBenchmark.testGetBytesString 1401994160926 thrpt 80 2621,683 38,270 ops/ms @GenerateMicroBenchmark public byte[] testGetBytesNative() { byte[] res = new byte[8]; long num = number; for(int i=7;i>=0;i--) { res[i] = (byte)(num & 255); num >>= 8; } return res; } @GenerateMicroBenchmark public byte[] testGetBytesString() { return Long.toString(number).getBytes(StandardCharsets.ISO_8859_1); } Gruss Bernd _______________________________________________ undertow-dev mailing list undertow-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/undertow-dev