Secured Hash Function Efficient hardware implementation by Liron Cohen Based on “LFSR-based Hashing and Authentication” by Hugo Krawvzyk (IBM)

LFSR-based Hash LFSR-based (Toeplitz) hashing, same as in RSS. Given a key of m bits returns hash value of n bits ( ). Guarantees that, Where. Note that in the (best) random case. In our framework of m=188b, n=32b we get, Where in the random case we get.

Example The secret key that generates this matrix is Compute the hash result via matrix multiplication :

Example Compute the hash value via our algorithm : Secret key Hash Result – Message –

Overview

Hash Type Advertises what message length should the hash expect, 4 options : 00IPv6 - message length is (2B+2B+16B+16B=) 36B 01IPv4 - message length is (2B+2B+4B+4B=) 12B 10Reduced IPv6 - message length is (2B+2B+16B+1B=) 21B 11Reduced IPv4 - message length is (2B+2B+4B+1B=) 9B

Seed Instead of generating pseudo-random bit sequence with LFSR we can receive a seed (secret key) from the firmware/driver. For IPv4 the seed should be (2B+2B+4B+4B+32b=) 16 Bytes long. For IPv6 the seed should be (2B+2B+16B+16B+32b=) 40 Bytes long. Note that the number should be generated by a LFSR with connections corresponding to the coefficients of an irreducible polynomial.

Mask Type Determines the output size in bits. Value between We will use different mask types for different uses, for example : On-die search – mask_type = (hash_result[10:0]) Off-die search for iScsi – mask_type = (hash_result[9:0]) Off-die search for RDMA – mask_type = (hash_result[16:0])

Timing Assuming low power, 65nm process, pipelined – Throughput of 1 hash result per cycle Latency of 4 cycles per hash result.

Implementation