[Cfrg] Trouble reproducing mulX_POLYVAL() test vector from RFC 8452 Appendix A
Tony Arcieri <bascule@gmail.com> Thu, 05 September 2019 20:05 UTC
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From: Tony Arcieri <bascule@gmail.com>
Date: Thu, 05 Sep 2019 13:04:46 -0700
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Subject: [Cfrg] Trouble reproducing mulX_POLYVAL() test vector from RFC 8452 Appendix A
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I've been trying to implement mulX_POLYVAL() as described in RFC 8452 Appendix A: https://tools.ietf.org/html/rfc8452#appendix-A It says: Given the 16-byte string 01000000000000000000000000000000, [...] mulX_POLYVAL of that string is 02000000000000000000000000000000. As a more general example, given 9c98c04df9387ded828175a92ba652d8, [...] mulX_POLYVAL of it is 3931819bf271fada0503eb52574ca5f2. However, I am getting 3931819bf271fada0503eb52574ca572 (highest bit unset). I'm not sure if it's a problem with my code, or the test vector. Here is the code. If I remove the "... ^ (hbhi << 63) ^ ..." from the last line of "mulx", it matches, but that seems like it wouldn't match POLYVAL's polynomial? Or is there something else I'm missing? #include <stdio.h> #include <stdint.h> static void mulx(uint64_t *lo, uint64_t *hi) { uint64_t hblo, hbhi; hblo = *lo >> 63; hbhi = *hi >> 63; *lo <<= 1; *hi <<= 1; *lo ^= hbhi; *hi ^= hblo ^ (hbhi << 63) ^ (hbhi << 62) ^ (hbhi << 57); } static uint64_t dec64le(const void *src) { const uint8_t *buf; int i; uint64_t x; buf = src; x = 0; for (i = 0; i < 8; i ++) { x |= (uint64_t)buf[i] << (8 * i); } return x; } static void enc64le(void *dst, uint64_t x) { uint8_t *buf; int i; buf = dst; for (i = 0; i < 8; i ++) { buf[i] = (uint8_t)(x >> (8 * i)); } } static void print128(const char *name, const void *src) { const uint8_t *buf; int i; printf("%s = ", name); buf = src; for (i = 0; i < 16; i ++) { printf("%02x", buf[i]); } printf("\n"); } int main(void) { /* * From RFC 8452: * * given 9c98c04df9387ded828175a92ba652d8, mulX_GHASH * of that string is 4e4c6026fc9c3ef6c140bad495d3296c and mulX_POLYVAL * of it is 3931819bf271fada0503eb52574ca5f2. */ static const uint8_t kat_in[] = { 0x9c, 0x98, 0xc0, 0x4d, 0xf9, 0x38, 0x7d, 0xed, 0x82, 0x81, 0x75, 0xa9, 0x2b, 0xa6, 0x52, 0xd8 }; uint64_t lo, hi; uint8_t tmp[16]; print128("in ", kat_in); lo = dec64le(kat_in); hi = dec64le(kat_in + 8); mulx(&lo, &hi); enc64le(tmp, lo); enc64le(tmp + 8, hi); print128("out", tmp); return 0; } -- Tony Arcieri
- [Cfrg] Trouble reproducing mulX_POLYVAL() test ve… Tony Arcieri
- Re: [Cfrg] Trouble reproducing mulX_POLYVAL() tes… Adam Langley
- Re: [Cfrg] Trouble reproducing mulX_POLYVAL() tes… Tony Arcieri
- Re: [Cfrg] Trouble reproducing mulX_POLYVAL() tes… Peter Gutmann