JH is a cryptographic hash function

Cryptographic hash function

A cryptographic hash function is a deterministic procedure that takes an arbitrary block of data and returns a fixed-size bit string, the hash value, such that an accidental or intentional change to the data will change the hash value...

 submitted to the NIST hash function competition

NIST hash function competition

The NIST hash function competition is an open competition held by the US National Institute of Standards and Technology for a new SHA-3 function to replace the older SHA-1 and SHA-2, which was formally announced in the Federal Register on November 2, 2007...

 by Hongjun Wu. JH was chosen as one of the five finalists of the competition. 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 (encryption function) to the state. This consists of 42 repetitions of:
   1. 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.
   2. Mix adjacent 4-bit blocks using a maximum distance separable code over GF(2⁴)
      Finite field
      In abstract algebra, a finite field or Galois field is a field that contains a finite number of elements. Finite fields are important in number theory, algebraic geometry, Galois theory, cryptography, and coding theory...
      
      .
   3. Permute 4-bit blocks so that they will be adjacent to different blocks in following rounds.
   4. The final half-round consists of an S-box substitution without a following MDS or permutation step.
3. XOR the input block into the right half of the state.

The resulting digest is the first 224, 256, 384 or 512 bits from the 1024-bit final value.
It is well suited to a bit slicing

Bit slicing

Bit slicing is a technique for constructing a processor from modules of smaller bit width. Each of these components processes one bit field or "slice" of an operand...

 implementation using the SSE2

SSE2

SSE2, Streaming SIMD Extensions 2, is one of the Intel SIMD processor supplementary instruction sets first introduced by Intel with the initial version of the Pentium 4 in 2001. It extends the earlier SSE instruction set, and is intended to fully supplant MMX. Intel extended SSE2 to create SSE3...

 instruction set, giving speeds of 16.8 Cycles per byte

Cycles per byte

Cycles per byte is a unit of measurement which indicates the number of clock cycles a microprocessor will perform per byte of data processed in an algorithm. It is commonly used as a partial indicator of real-world performance in cryptographic functions....

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External links

• The JH web site
• JH page on the SHA-3 Zoo
• A VHDL source codes developed in the Cryptographic Engineering Research Group (CERG) at George Mason University