JH (hash function)


JH is a cryptographic [hash function] submitted to the NIST hash function competition by Hongjun Wu. Though chosen as one of the five finalists of the competition, in 2012 JH ultimately lost to NIST hash candidate Keccak. JH has a 1024-bit state, and works on 512-bit input blocks. Processing an input block consists of three steps:
  1. XOR the input block into the left half of the state.
  2. Apply a 42-round unkeyed permutation to the state. This consists of 42 repetitions of:
  3. # Break the input into 256 4-bit blocks, and map each through one of two 4-bit S-boxes, the choice being made by a 256-bit round-dependent key schedule. Equivalently, combine each input block with a key bit, and map the result through a 5→4 bit S-box.
  4. # Mix adjacent 4-bit blocks using a maximum distance separable code over GF(24).
  5. # Permute 4-bit blocks so that they will be adjacent to different blocks in following rounds.
  6. XOR the input block into the right half of the state.
The resulting digest is the last 224, 256, 384 or 512 bits from the 1024-bit final value.
It is well suited to a bit slicing implementation using the SSE2 instruction set, giving speeds of 16.8 cycles per byte.

Examples of JH hashes

Hash values of empty string.
JH-224
0x 2c99df889b019309051c60fecc2bd285a774940e43175b76b2626630
JH-256
0x 46e64619c18bb0a92a5e87185a47eef83ca747b8fcc8e1412921357e326df434
JH-384
0x 2fe5f71b1b3290d3c017fb3c1a4d02a5cbeb03a0476481e25082434a881994b0ff99e078d2c16b105ad069b569315328
JH-512
0x 90ecf2f76f9d2c8017d979ad5ab96b87d58fc8fc4b83060f3f900774faa2c8fabe69c5f4ff1ec2b61d6b316941cedee117fb04b1f4c5bc1b919ae841c50eec4f
Even a small change in the message will result in a mostly different hash, due to the avalanche effect. For example, adding a period to the end of the sentence:
JH-256
0x 6a049fed5fc6874acfdc4a08b568a4f8cbac27de933496f031015b38961608a0
JH-256
0x d001ae2315421c5d3272bac4f4aa524bddd207530d5d26bbf51794f0da18fafc