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

2. 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.

3. Example The secret key that generates this matrix is 100110. Compute the hash result via matrix multiplication :

4. Example Compute the hash value via our algorithm : Secret key - 1 0 0 1 1 0 Hash Result – Message – 1 1 0 1 0 0 01 0 01 0 10 1 1

5. Overview

6. 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

7. 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.

8. Mask Type Determines the output size in bits. Value between 1-31. We will use different mask types for different uses, for example : On-die search – mask_type = 01011 (hash_result[10:0]) Off-die search for iScsi – mask_type = 01001 (hash_result[9:0]) Off-die search for RDMA – mask_type = 10001 (hash_result[16:0])

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

10. Implementation