Simple hashing function

Hello, I am looking for a simple (few lines to implement) hashing function to reduce a 128 bit integer to 64 bits.

I want to use the hash to derive a 64 bit IPv6 host address from a 128 bit CPU ID.

I want all of the bits of the CPUID to affect the result, instead of just grabbing the top/bottom 8 bytes of the ID. I'm guessing there are lots of options for hashes, but many are made to generate hashes from much longer messages than 128 bit.

Any suggestions?

Best regards, Joakim Gebart Eistec AB

Hey Joakim, There is already a collection of hashing implementations in sys/include/hashes.h. Unfortunally all of them yield 32 bit integers. I did however also used the CPU ID and djb2_hash() in [1] to initialize an IEEE 802.15.4 device’s EUI-64 - which is the link-layer pendent to the IPv6 host suffix [2] - by spliting the CPU ID in half, generating a 32-bit hash from each half and splicing them together again as a 64-bit number.

Best regards, Martine

[1] [2]

Good idea about splitting the CPUID into two halves. I'll try that, thank you! Joakim Gebart Managing Director Eistec AB

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