| 1 | [[tags: egg]] |
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| 2 | |
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| 3 | == siphash |
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| 4 | |
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| 5 | [[toc:]] |
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| 6 | |
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| 7 | == Description |
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| 8 | |
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| 9 | A Scheme implementation of the SipHash family of hash functions. |
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| 10 | |
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| 11 | [[http://131002.net/siphash|SipHash]] is a cryptographically strong family of hash functions designed by Jean-Philippe Aumasson and Daniel J. Bernstein. |
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| 12 | |
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| 13 | The source for this extension is available [[http://git.foldling.org/siphash.git|here]]. |
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| 14 | |
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| 15 | == Requirements |
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| 16 | |
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| 17 | * [[http://wiki.call-cc.org/egg/numbers|numbers]] |
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| 18 | |
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| 19 | == API |
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| 20 | |
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| 21 | Three functions are provided: |
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| 22 | |
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| 23 | * {{make-siphash}} |
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| 24 | * {{siphash-2-4}} |
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| 25 | * {{siphash-4-8}} |
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| 26 | |
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| 27 | <procedure>(make-siphash c d) => procedure</procedure> |
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| 28 | |
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| 29 | {{make-siphash}} constructs a hashing function. |
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| 30 | |
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| 31 | It takes two positive integer arguments {{c}} and {{d}} and returns a hashing procedure with that many compression and finalization rounds, respectively. |
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| 32 | |
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| 33 | The returned procedure's signature matches those of {{siphash-2-4}} and {{siphash-4-8}}. |
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| 34 | |
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| 35 | <procedure>(siphash-2-4 key) => (procedure message) => integer</procedure> |
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| 36 | <procedure>(siphash-2-4 key message) => integer</procedure> |
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| 37 | <procedure>(siphash-4-8 key) => (procedure message) => integer</procedure> |
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| 38 | <procedure>(siphash-4-8 key message) => integer</procedure> |
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| 39 | |
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| 40 | {{siphash-2-4}} and {{siphash-4-8}} are predefined hashing procedures. |
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| 41 | |
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| 42 | Each takes one or two SRFI-4 u8vector arguments, the key and message to hash, and returns a positive integer. {{key}} should have a length of 16, while {{message}} may be any length. If {{message}} isn't given, a prekeyed hashing function is returned. |
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| 43 | |
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| 44 | The SipHash specification recommends SipHash-2-4 for performance and SipHash-4-8 for cryptographic security. |
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| 45 | |
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| 46 | == Examples |
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| 47 | |
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| 48 | <enscript highlight=scheme> |
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| 49 | > (define string->u8vector (compose blob->u8vector string->blob)) |
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| 50 | > (define key (u8vector 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15)) |
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| 51 | > (define msg (string->u8vector "The rain in Spain falls mainly on the plain.")) |
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| 52 | |
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| 53 | > (siphash-2-4 key msg) |
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| 54 | ; => 8751579407287093977 |
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| 55 | |
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| 56 | > ((siphash-4-8 key) msg) |
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| 57 | ; => 13472556437817646137 |
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| 58 | |
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| 59 | > ((make-siphash 8 16) |
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| 60 | key |
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| 61 | (string->u8vector |
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| 62 | "In Hertford, Hereford and Hampshire, hurricanes hardly ever happen.")) |
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| 63 | ; => 9275736844991428064 |
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| 64 | </enscript> |
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| 65 | |
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| 66 | == Author |
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| 67 | |
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| 68 | Evan Hanson |
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| 69 | |
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| 70 | == License |
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| 71 | |
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| 72 | Copyright (c) 2013-2018, Evan Hanson, 3-Clause BSD License. |
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