From afb0962761603763f8a0c30e928a3c011a9f03e8 Mon Sep 17 00:00:00 2001 From: Emman Date: Tue, 19 Jan 2021 14:23:56 +0800 Subject: [PATCH] MAGIC - first version of SM2 P256 curve --- sm2/p256.go | 1377 ++++++++++++++++++++++++++++++++++++++++++++++- sm2/sm2_test.go | 21 +- sm2/util.go | 4 +- 3 files changed, 1393 insertions(+), 9 deletions(-) diff --git a/sm2/p256.go b/sm2/p256.go index c581398..c1b8ddf 100644 --- a/sm2/p256.go +++ b/sm2/p256.go @@ -2,27 +2,43 @@ package sm2 import ( "crypto/elliptic" + "fmt" "math/big" "sync" ) +// See https://www.imperialviolet.org/2010/12/04/ecc.html ([1]) for background. + type p256Curve struct { *elliptic.CurveParams } var ( - p256 p256Curve + p256 p256Curve + + // RInverse contains 1/R mod p - the inverse of the Montgomery constant + // (2**257). + p256RInverse *big.Int + initonce sync.Once ) func initP256() { p256.CurveParams = &elliptic.CurveParams{Name: "P-256/SM2"} + // 2**256 - 2**224 - 2**96 + 2**64 - 1 p256.P, _ = new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF", 16) p256.N, _ = new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123", 16) p256.B, _ = new(big.Int).SetString("28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93", 16) p256.Gx, _ = new(big.Int).SetString("32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7", 16) p256.Gy, _ = new(big.Int).SetString("BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0", 16) p256.BitSize = 256 + + // ModeInverse(2**257, P) + // p256RInverse = big.NewInt(0) + // r, _ := new(big.Int).SetString("20000000000000000000000000000000000000000000000000000000000000000", 16) + // p256RInverse.ModInverse(r, p256.P) + // fmt.Printf("%s\n", hex.EncodeToString(p256RInverse.Bytes())) + p256RInverse, _ = new(big.Int).SetString("7ffffffd80000002fffffffe000000017ffffffe800000037ffffffc80000002", 16) } // P256 init and return the singleton @@ -30,3 +46,1362 @@ func P256() elliptic.Curve { initonce.Do(initP256) return p256 } + +func (curve p256Curve) Params() *elliptic.CurveParams { + return curve.CurveParams +} + +// p256GetScalar endian-swaps the big-endian scalar value from in and writes it +// to out. If the scalar is equal or greater than the order of the group, it's +// reduced modulo that order. +func p256GetScalar(out *[32]byte, in []byte) { + n := new(big.Int).SetBytes(in) + var scalarBytes []byte + + if n.Cmp(p256.N) >= 0 { + n.Mod(n, p256.N) + scalarBytes = n.Bytes() + } else { + scalarBytes = in + } + + for i, v := range scalarBytes { + out[len(scalarBytes)-(1+i)] = v + } +} + +func (p256Curve) ScalarBaseMult(scalar []byte) (x, y *big.Int) { + var scalarReversed [32]byte + p256GetScalar(&scalarReversed, scalar) + + var x1, y1, z1 [p256Limbs]uint32 + p256ScalarBaseMult(&x1, &y1, &z1, &scalarReversed) + return p256ToAffine(&x1, &y1, &z1) +} + +func (p256Curve) ScalarMult(bigX, bigY *big.Int, scalar []byte) (x, y *big.Int) { + var scalarReversed [32]byte + p256GetScalar(&scalarReversed, scalar) + + var px, py, x1, y1, z1 [p256Limbs]uint32 + p256FromBig(&px, bigX) + p256FromBig(&py, bigY) + p256ScalarMult(&x1, &y1, &z1, &px, &py, &scalarReversed) + return p256ToAffine(&x1, &y1, &z1) +} + +// Field elements are represented as nine, unsigned 32-bit words. +// +// The value of a field element is: +// x[0] + (x[1] * 2**29) + (x[2] * 2**57) + (x[3] * 2**86) + (x[4] * 2**114) + (x[5] * 2**143) + (x[6] * 2**171) + (x[7] * 2**200) + (x[8] * 2**228) +// +// That is, each limb is alternately 29 or 28-bits wide in little-endian +// order. +// +// This means that a field element hits 2**257, rather than 2**256 as we would +// like. A 28, 29, ... pattern would cause us to hit 2**256, but that causes +// problems when multiplying as terms end up one bit short of a limb which +// would require much bit-shifting to correct. +// +// Finally, the values stored in a field element are in Montgomery form. So the +// value |y| is stored as (y*R) mod p, where p is the P-256 prime and R is +// 2**257. + +const ( + p256Limbs = 9 + bottom28Bits = 0xfffffff + bottom29Bits = 0x1fffffff +) + +var ( + // p256One is the number 1 as a field element. + p256One = [p256Limbs]uint32{2, 0, 0x1fffff00, 0x7ff, 0, 0, 0, 0x2000000, 0} + p256Zero = [p256Limbs]uint32{0, 0, 0, 0, 0, 0, 0, 0, 0} + // p256P is the prime modulus as a field element. + p256P = [p256Limbs]uint32{0x1fffffff, 0xfffffff, 0x7f, 0xffffc00, 0x1fffffff, 0xfffffff, 0x1fffffff, 0xeffffff, 0xfffffff} + // p2562P is the twice prime modulus as a field element. + p2562P = [p256Limbs]uint32{0x1ffffffe, 0xfffffff, 0xff, 0xffff800, 0x1fffffff, 0xfffffff, 0x1fffffff, 0xdffffff, 0x1fffffff} + // p256b is the curve param b as a field element + p256b = [p256Limbs]uint32{0x1781ba84, 0xd230632, 0x1537ab90, 0x9bcd74d, 0xe1e38e7, 0x5417a94, 0x12149e60, 0x17441c5, 0x481fc31} +) + +// p256Precomputed contains precomputed values to aid the calculation of scalar +// multiples of the base point, G. It's actually two, equal length, tables +// concatenated. +// +// The first table contains (x,y) field element pairs for 16 multiples of the +// base point, G. +// +// Index | Index (binary) | Value +// 0 | 0000 | 0G (all zeros, omitted) +// 1 | 0001 | G +// 2 | 0010 | 2**64G +// 3 | 0011 | 2**64G + G +// 4 | 0100 | 2**128G +// 5 | 0101 | 2**128G + G +// 6 | 0110 | 2**128G + 2**64G +// 7 | 0111 | 2**128G + 2**64G + G +// 8 | 1000 | 2**192G +// 9 | 1001 | 2**192G + G +// 10 | 1010 | 2**192G + 2**64G +// 11 | 1011 | 2**192G + 2**64G + G +// 12 | 1100 | 2**192G + 2**128G +// 13 | 1101 | 2**192G + 2**128G + G +// 14 | 1110 | 2**192G + 2**128G + 2**64G +// 15 | 1111 | 2**192G + 2**128G + 2**64G + G +// +// The second table follows the same style, but the terms are 2**32G, +// 2**96G, 2**160G, 2**224G. +// 16 | 10000 | 2**32G +// 17 | 10010 | 2**96G +// 18 | 10001 | 2**96G + 2**32G +// 19 | 10011 | 2**160G +// 20 | 10100 | 2**160G + 2**32G +// 21 | 10101 | 2**160G + 2**96G +// 22 | 10110 | 2**160G + 2**96G + 2**32G +// 23 | 10111 | 2**224G +// 24 | 11000 | 2**224G + 2**32G +// 25 | 11001 | 2**224G + 2**96G +// 26 | 11011 | 2**224G + 2**96G + 2**32G +// 27 | 11100 | 2**224G + 2**160G +// 28 | 11101 | 2**224G + 2**160G + 2**32G +// 29 | 11110 | 2**224G + 2**160G + 2**96G +// 30 | 11111 | 2**224G + 2**160G + 2**96G + 2**32G +// This is ~2KB of data. +// precompute(1) +// precompute(2**32) +var p256Precomputed = [p256Limbs * 2 * 15 * 2]uint32{ + 0x830053d, 0x328990f, 0x6c04fe1, 0xc0f72e5, 0x1e19f3c, 0x666b093, 0x175a87b, 0xec38276, 0x222cf4b, + 0x185a1bba, 0x354e593, 0x1295fac1, 0xf2bc469, 0x47c60fa, 0xc19b8a9, 0xf63533e, 0x903ae6b, 0xc79acba, + 0x15b061a4, 0x33e020b, 0xdffb34b, 0xfcf2c8, 0x16582e08, 0x262f203, 0xfb34381, 0xa55452, 0x604f0ff, + 0x41f1f90, 0xd64ced2, 0xee377bf, 0x75f05f0, 0x189467ae, 0xe2244e, 0x1e7700e8, 0x3fbc464, 0x9612d2e, + 0x1341b3b8, 0xee84e23, 0x1edfa5b4, 0x14e6030, 0x19e87be9, 0x92f533c, 0x1665d96c, 0x226653e, 0xa238d3e, + 0xf5c62c, 0x95bb7a, 0x1f0e5a41, 0x28789c3, 0x1f251d23, 0x8726609, 0xe918910, 0x8096848, 0xf63d028, + 0x152296a1, 0x9f561a8, 0x14d376fb, 0x898788a, 0x61a95fb, 0xa59466d, 0x159a003d, 0x1ad1698, 0x93cca08, + 0x1b314662, 0x706e006, 0x11ce1e30, 0x97b710, 0x172fbc0d, 0x8f50158, 0x11c7ffe7, 0xd182cce, 0xc6ad9e8, + 0x12ea31b2, 0xc4e4f38, 0x175b0d96, 0xec06337, 0x75a9c12, 0xb001fdf, 0x93e82f5, 0x34607de, 0xb8035ed, + 0x17f97924, 0x75cf9e6, 0xdceaedd, 0x2529924, 0x1a10c5ff, 0xb1a54dc, 0x19464d8, 0x2d1997, 0xde6a110, + 0x1e276ee5, 0x95c510c, 0x1aca7c7a, 0xfe48aca, 0x121ad4d9, 0xe4132c6, 0x8239b9d, 0x40ea9cd, 0x816c7b, + 0x632d7a4, 0xa679813, 0x5911fcf, 0x82b0f7c, 0x57b0ad5, 0xbef65, 0xd541365, 0x7f9921f, 0xc62e7a, + 0x3f4b32d, 0x58e50e1, 0x6427aed, 0xdcdda67, 0xe8c2d3e, 0x6aa54a4, 0x18df4c35, 0x49a6a8e, 0x3cd3d0c, + 0xd7adf2, 0xcbca97, 0x1bda5f2d, 0x3258579, 0x606b1e6, 0x6fc1b5b, 0x1ac27317, 0x503ca16, 0xa677435, + 0x57bc73, 0x3992a42, 0xbab987b, 0xfab25eb, 0x128912a4, 0x90a1dc4, 0x1402d591, 0x9ffbcfc, 0xaa48856, + 0x7a7c2dc, 0xcefd08a, 0x1b29bda6, 0xa785641, 0x16462d8c, 0x76241b7, 0x79b6c3b, 0x204ae18, 0xf41212b, + 0x1f567a4d, 0xd6ce6db, 0xedf1784, 0x111df34, 0x85d7955, 0x55fc189, 0x1b7ae265, 0xf9281ac, 0xded7740, + 0xf19468b, 0x83763bb, 0x8ff7234, 0x3da7df8, 0x9590ac3, 0xdc96f2a, 0x16e44896, 0x7931009, 0x99d5acc, + 0x10f7b842, 0xaef5e84, 0xc0310d7, 0xdebac2c, 0x2a7b137, 0x4342344, 0x19633649, 0x3a10624, 0x4b4cb56, + 0x1d809c59, 0xac007f, 0x1f0f4bcd, 0xa1ab06e, 0xc5042cf, 0x82c0c77, 0x76c7563, 0x22c30f3, 0x3bf1568, + 0x7a895be, 0xfcca554, 0x12e90e4c, 0x7b4ab5f, 0x13aeb76b, 0x5887e2c, 0x1d7fe1e3, 0x908c8e3, 0x95800ee, + 0xb36bd54, 0xf08905d, 0x4e73ae8, 0xf5a7e48, 0xa67cb0, 0x50e1067, 0x1b944a0a, 0xf29c83a, 0xb23cfb9, + 0xbe1db1, 0x54de6e8, 0xd4707f2, 0x8ebcc2d, 0x2c77056, 0x1568ce4, 0x15fcc849, 0x4069712, 0xe2ed85f, + 0x2c5ff09, 0x42a6929, 0x628e7ea, 0xbd5b355, 0xaf0bd79, 0xaa03699, 0xdb99816, 0x4379cef, 0x81d57b, + 0x11237f01, 0xe2a820b, 0xfd53b95, 0x6beb5ee, 0x1aeb790c, 0xe470d53, 0x2c2cfee, 0x1c1d8d8, 0xa520fc4, + 0x1518e034, 0xa584dd4, 0x29e572b, 0xd4594fc, 0x141a8f6f, 0x8dfccf3, 0x5d20ba3, 0x2eb60c3, 0x9f16eb0, + 0x11cec356, 0xf039f84, 0x1b0990c1, 0xc91e526, 0x10b65bae, 0xf0616e8, 0x173fa3ff, 0xec8ccf9, 0xbe32790, + 0x11da3e79, 0xe2f35c7, 0x908875c, 0xdacf7bd, 0x538c165, 0x8d1487f, 0x7c31aed, 0x21af228, 0x7e1689d, + 0xdfc23ca, 0x24f15dc, 0x25ef3c4, 0x35248cd, 0x99a0f43, 0xa4b6ecc, 0xd066b3, 0x2481152, 0x37a7688, + 0x15a444b6, 0xb62300c, 0x4b841b, 0xa655e79, 0xd53226d, 0xbeb348a, 0x127f3c2, 0xb989247, 0x71a277d, + 0x19e9dfcb, 0xb8f92d0, 0xe2d226c, 0x390a8b0, 0x183cc462, 0x7bd8167, 0x1f32a552, 0x5e02db4, 0xa146ee9, + 0x1a003957, 0x1c95f61, 0x1eeec155, 0x26f811f, 0xf9596ba, 0x3082bfb, 0x96df083, 0x3e3a289, 0x7e2d8be, + 0x157a63e0, 0x99b8941, 0x1da7d345, 0xcc6cd0, 0x10beed9a, 0x48e83c0, 0x13aa2e25, 0x7cad710, 0x4029988, + 0x13dfa9dd, 0xb94f884, 0x1f4adfef, 0xb88543, 0x16f5f8dc, 0xa6a67f4, 0x14e274e2, 0x5e56cf4, 0x2f24ef, + 0x1e9ef967, 0xfe09bad, 0xfe079b3, 0xcc0ae9e, 0xb3edf6d, 0x3e961bc, 0x130d7831, 0x31043d6, 0xba986f9, + 0x1d28055, 0x65240ca, 0x4971fa3, 0x81b17f8, 0x11ec34a5, 0x8366ddc, 0x1471809, 0xfa5f1c6, 0xc911e15, + 0x8849491, 0xcf4c2e2, 0x14471b91, 0x39f75be, 0x445c21e, 0xf1585e9, 0x72cc11f, 0x4c79f0c, 0xe5522e1, + 0x1874c1ee, 0x4444211, 0x7914884, 0x3d1b133, 0x25ba3c, 0x4194f65, 0x1c0457ef, 0xac4899d, 0xe1fa66c, + 0x130a7918, 0x9b8d312, 0x4b1c5c8, 0x61ccac3, 0x18c8aa6f, 0xe93cb0a, 0xdccb12c, 0xde10825, 0x969737d, + 0xf58c0c3, 0x7cee6a9, 0xc2c329a, 0xc7f9ed9, 0x107b3981, 0x696a40e, 0x152847ff, 0x4d88754, 0xb141f47, + 0x5a16ffe, 0x3a7870a, 0x18667659, 0x3b72b03, 0xb1c9435, 0x9285394, 0xa00005a, 0x37506c, 0x2edc0bb, + 0x19afe392, 0xeb39cac, 0x177ef286, 0xdf87197, 0x19f844ed, 0x31fe8, 0x15f9bfd, 0x80dbec, 0x342e96e, + 0x497aced, 0xe88e909, 0x1f5fa9ba, 0x530a6ee, 0x1ef4e3f1, 0x69ffd12, 0x583006d, 0x2ecc9b1, 0x362db70, + 0x18c7bdc5, 0xf4bb3c5, 0x1c90b957, 0xf067c09, 0x9768f2b, 0xf73566a, 0x1939a900, 0x198c38a, 0x202a2a1, + 0x4bbf5a6, 0x4e265bc, 0x1f44b6e7, 0x185ca49, 0xa39e81b, 0x24aff5b, 0x4acc9c2, 0x638bdd3, 0xb65b2a8, + 0x6def8be, 0xb94537a, 0x10b81dee, 0xe00ec55, 0x2f2cdf7, 0xc20622d, 0x2d20f36, 0xe03c8c9, 0x898ea76, + 0x8e3921b, 0x8905bff, 0x1e94b6c8, 0xee7ad86, 0x154797f2, 0xa620863, 0x3fbd0d9, 0x1f3caab, 0x30c24bd, + 0x19d3892f, 0x59c17a2, 0x1ab4b0ae, 0xf8714ee, 0x90c4098, 0xa9c800d, 0x1910236b, 0xea808d3, 0x9ae2f31, + 0x1a15ad64, 0xa48c8d1, 0x184635a4, 0xb725ef1, 0x11921dcc, 0x3f866df, 0x16c27568, 0xbdf580a, 0xb08f55c, + 0x186ee1c, 0xb1627fa, 0x34e82f6, 0x933837e, 0xf311be5, 0xfedb03b, 0x167f72cd, 0xa5469c0, 0x9c82531, + 0xb92a24b, 0x14fdc8b, 0x141980d1, 0xbdc3a49, 0x7e02bb1, 0xaf4e6dd, 0x106d99e1, 0xd4616fc, 0x93c2717, + 0x1c0a0507, 0xc6d5fed, 0x9a03d8b, 0xa1d22b0, 0x127853e3, 0xc4ac6b8, 0x1a048cf7, 0x9afb72c, 0x65d485d, + 0x72d5998, 0xe9fa744, 0xe49e82c, 0x253cf80, 0x5f777ce, 0xa3799a5, 0x17270cbb, 0xc1d1ef0, 0xdf74977, + 0x114cb859, 0xfa8e037, 0xb8f3fe5, 0xc734cc6, 0x70d3d61, 0xeadac62, 0x12093dd0, 0x9add67d, 0x87200d6, + 0x175bcbb, 0xb29b49f, 0x1806b79c, 0x12fb61f, 0x170b3a10, 0x3aaf1cf, 0xa224085, 0x79d26af, 0x97759e2, + 0x92e19f1, 0xb32714d, 0x1f00d9f1, 0xc728619, 0x9e6f627, 0xe745e24, 0x18ea4ace, 0xfc60a41, 0x125f5b2, + 0xc3cf512, 0x39ed486, 0xf4d15fa, 0xf9167fd, 0x1c1f5dd5, 0xc21a53e, 0x1897930, 0x957a112, 0x21059a0, + 0x1f9e3ddc, 0xa4dfced, 0x8427f6f, 0x726fbe7, 0x1ea658f8, 0x2fdcd4c, 0x17e9b66f, 0xb2e7c2e, 0x39923bf, + 0x1bae104, 0x3973ce5, 0xc6f264c, 0x3511b84, 0x124195d7, 0x11996bd, 0x20be23d, 0xdc437c4, 0x4b4f16b, + 0x11902a0, 0x6c29cc9, 0x1d5ffbe6, 0xdb0b4c7, 0x10144c14, 0x2f2b719, 0x301189, 0x2343336, 0xa0bf2ac, +} + +func precompute(params *elliptic.CurveParams, base *big.Int) { + // 1/32/64/96/128/160/192/224 + var values [4]*big.Int + + values[0] = base + for i := 1; i < 4; i++ { + values[i] = new(big.Int) + values[i].Lsh(values[i-1], 64) + } + for i := 0; i < 4; i++ { + x, y := params.ScalarBaseMult(values[i].Bytes()) + printPoint(params, x, y) + v := new(big.Int) + switch i { + case 1: + v.Add(values[0], values[1]) + x, y := params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + case 2: + v.Add(values[0], values[2]) + x, y := params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(values[1], values[2]) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(values[0], v) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + case 3: + v.Add(values[0], values[3]) + x, y := params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(values[1], values[3]) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(values[0], v) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(values[2], values[3]) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(values[0], v) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(values[2], values[3]) + v.Add(v, values[1]) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + v.Add(v, values[0]) + x, y = params.ScalarBaseMult(v.Bytes()) + printPoint(params, x, y) + } + } +} + +func printPoint(params *elliptic.CurveParams, x, y *big.Int) { + var out [p256Limbs]uint32 + p256FromBigAgainstP(&out, x, params.P) + printp256Limbs(&out) + p256FromBigAgainstP(&out, y, params.P) + printp256Limbs(&out) +} + +func printp256Limbs(one *[p256Limbs]uint32) { + for i := 0; i < p256Limbs; i++ { + fmt.Printf("0x%x, ", one[i]) + } + fmt.Println() +} + +func print1to7(params *elliptic.CurveParams) { + var out [p256Limbs]uint32 + for i := 1; i < 8; i++ { + value := big.NewInt(int64(i)) + p256FromBigAgainstP(&out, value, params.P) + printp256Limbs(&out) + } +} + +// Field element operations: + +// nonZeroToAllOnes returns: +// 0xffffffff for 0 < x <= 2**31 +// 0 for x == 0 or x > 2**31. +func nonZeroToAllOnes(x uint32) uint32 { + return ((x - 1) >> 31) - 1 +} + +// p256ReduceCarry adds a multiple of p in order to cancel |carry|, +// which is a term at 2**257. +// +// On entry: carry < 2**3, inout[0,2,...] < 2**29, inout[1,3,...] < 2**28. +// On exit: inout[0,2,..] < 2**30, inout[1,3,...] < 2**29. +func p256ReduceCarry(inout *[p256Limbs]uint32, carry uint32) { + carry_mask := nonZeroToAllOnes(carry) + inout[0] += carry << 1 + // 2**30 = 0x40000000, this doesn't underflow + inout[2] -= carry << 8 + inout[2] += 0x20000000 & carry_mask + + inout[3] -= 1 & carry_mask + inout[3] += carry << 11 + + // 2**29 = 0x20000000, this doesn't underflow: 0xfffffff + 0x2000000 = 0x11ffffff < 0x20000000 + inout[7] += carry << 25 +} + +// p256Sum sets out = in+in2. +// +// On entry, in[i]+in2[i] must not overflow a 32-bit word. +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29 +func p256Sum(out, in, in2 *[p256Limbs]uint32) { + carry := uint32(0) + for i := 0; ; i++ { + out[i] = in[i] + in2[i] + out[i] += carry + carry = out[i] >> 29 + out[i] &= bottom29Bits + + i++ + if i == p256Limbs { + break + } + + out[i] = in[i] + in2[i] + out[i] += carry + carry = out[i] >> 28 + out[i] &= bottom28Bits + } + + p256ReduceCarry(out, carry) +} + +// p256Zero31 is 0 mod p. +// {two31m3, two30m2, two31p10m2, two30m13m2, two31m2, two30m2, two31m2, two30m27m2, two31m2} +var p256Zero31 = [p256Limbs]uint32{0x7FFFFFF8, 0x3FFFFFFC, 0x800003FC, 0x3FFFDFFC, 0x7FFFFFFC, 0x3FFFFFFC, 0x7FFFFFFC, 0x37FFFFFC, 0x7FFFFFFC} + +func limbsToBig(in *[p256Limbs]uint32) *big.Int { + result, tmp := new(big.Int), new(big.Int) + + result.SetInt64(int64(in[p256Limbs-1])) + for i := p256Limbs - 2; i >= 0; i-- { + if (i & 1) == 0 { + result.Lsh(result, 29) + } else { + result.Lsh(result, 28) + } + tmp.SetInt64(int64(in[i])) + result.Add(result, tmp) + } + return result +} + +// p256GetZero31, the func to calucate p256Zero31 +func p256GetZero31(out *[p256Limbs]uint32) { + tmp := big.NewInt(0) + result := limbsToBig(&[p256Limbs]uint32{1 << 31, 1 << 30, 1 << 31, 1 << 30, 1 << 31, 1 << 30, 1 << 31, 1 << 30, 1 << 31}) + tmp = tmp.Mod(result, p256.P) + tmp = tmp.Sub(result, tmp) + for i := 0; i < 9; i++ { + if bits := tmp.Bits(); len(bits) > 0 { + out[i] = uint32(bits[0]) & 0x7fffffff + if out[i] < 0x70000000 { + out[i] += 0x80000000 + } + } else { + out[i] = 0x80000000 + } + tmp.Sub(tmp, big.NewInt(int64(out[i]))) + tmp.Rsh(tmp, 29) + i++ + if i == p256Limbs { + break + } + + if bits := tmp.Bits(); len(bits) > 0 { + out[i] = uint32(bits[0]) & 0x3fffffff + if out[i] < 0x30000000 { + out[i] += 0x40000000 + } + } else { + out[i] = 0x40000000 + } + tmp.Sub(tmp, big.NewInt(int64(out[i]))) + tmp.Rsh(tmp, 28) + } +} + +// p256Diff sets out = in-in2. +// +// On entry: in[0,2,...] < 2**30, in[1,3,...] < 2**29 and +// in2[0,2,...] < 2**30, in2[1,3,...] < 2**29. +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +func p256Diff(out, in, in2 *[p256Limbs]uint32) { + var carry uint32 + + for i := 0; ; i++ { + out[i] = in[i] - in2[i] + out[i] += p256Zero31[i] + out[i] += carry + carry = out[i] >> 29 + out[i] &= bottom29Bits + i++ + if i == p256Limbs { + break + } + + out[i] = in[i] - in2[i] + out[i] += p256Zero31[i] + out[i] += carry + carry = out[i] >> 28 + out[i] &= bottom28Bits + } + + p256ReduceCarry(out, carry) +} + +// p256ReduceDegree sets out = tmp/R mod p where tmp contains 64-bit words with +// the same 29,28,... bit positions as a field element. +// +// The values in field elements are in Montgomery form: x*R mod p where R = +// 2**257. Since we just multiplied two Montgomery values together, the result +// is x*y*R*R mod p. We wish to divide by R in order for the result also to be +// in Montgomery form. +// +// On entry: tmp[i] < 2**64 +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29 +func p256ReduceDegree(out *[p256Limbs]uint32, tmp [17]uint64) { + // The following table may be helpful when reading this code: + // + // Limb number: 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10... + // Width (bits): 29| 28| 29| 28| 29| 28| 29| 28| 29| 28| 29 + // Start bit: 0 | 29| 57| 86|114|143|171|200|228|257|285 + // (odd phase): 0 | 28| 57| 85|114|142|171|199|228|256|285 + var tmp2 [18]uint32 + var carry, x, xMask uint32 + + // tmp contains 64-bit words with the same 29,28,29-bit positions as an + // field element. So the top of an element of tmp might overlap with + // another element two positions down. The following loop eliminates + // this overlap. + tmp2[0] = uint32(tmp[0]) & bottom29Bits + + tmp2[1] = uint32(tmp[0]) >> 29 + tmp2[1] |= (uint32(tmp[0]>>32) << 3) & bottom28Bits + tmp2[1] += uint32(tmp[1]) & bottom28Bits + carry = tmp2[1] >> 28 + tmp2[1] &= bottom28Bits + + for i := 2; i < 17; i++ { + tmp2[i] = (uint32(tmp[i-2] >> 32)) >> 25 + tmp2[i] += (uint32(tmp[i-1])) >> 28 + tmp2[i] += (uint32(tmp[i-1]>>32) << 4) & bottom29Bits + tmp2[i] += uint32(tmp[i]) & bottom29Bits + tmp2[i] += carry + carry = tmp2[i] >> 29 + tmp2[i] &= bottom29Bits + + i++ + if i == 17 { + break + } + tmp2[i] = uint32(tmp[i-2]>>32) >> 25 + tmp2[i] += uint32(tmp[i-1]) >> 29 + tmp2[i] += ((uint32(tmp[i-1] >> 32)) << 3) & bottom28Bits + tmp2[i] += uint32(tmp[i]) & bottom28Bits + tmp2[i] += carry + carry = tmp2[i] >> 28 + tmp2[i] &= bottom28Bits + } + + tmp2[17] = uint32(tmp[15]>>32) >> 25 + tmp2[17] += uint32(tmp[16]) >> 29 + tmp2[17] += uint32(tmp[16]>>32) << 3 + tmp2[17] += carry + + // Montgomery elimination of terms: + // + // Since R is 2**257, we can divide by R with a bitwise shift if we can + // ensure that the right-most 257 bits are all zero. We can make that true + // by adding multiplies of p without affecting the value. + // + // So we eliminate limbs from right to left. Since the bottom 29 bits of p + // are all ones, then by adding tmp2[0]*p to tmp2 we'll make tmp2[0] == 0. + // We can do that for 8 further limbs and then right shift to eliminate the + // extra factor of R. + for i := 0; ; i += 2 { + tmp2[i+1] += tmp2[i] >> 29 + x = tmp2[i] & bottom29Bits + xMask = nonZeroToAllOnes(x) + tmp2[i] = 0 + + // The bounds calculations for this loop are tricky. Each iteration of + // the loop eliminates two words by adding values to words to their + // right. + // + // The following table contains the amounts added to each word (as an + // offset from the value of i at the top of the loop). The amounts are + // accounted for from the first and second half of the loop separately + // and are written as, for example, 28 to mean a value <2**28. + // + // Word: 2 3 4 5 6 7 8 9 10 + // Added in top half: 29 28 29 29 29 29 29 28 + // 29 28 29 28 29 + // 29 + // Added in bottom half: 28 29 28 28 28 29 28 28 + // 28 29 28 29 28 + // + // + // The following table accumulates these values. The sums at the bottom + // are written as, for example, 29+28, to mean a value < 2**29+2**28. + // + // Word: 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 + // 29 28 29 29 29 29 29 28 28 28 28 28 28 28 28 28 + // 28 29 28 29 28 29 28 29 28 29 28 29 28 29 + // 29 28 28 28 29 28 29 28 29 28 29 28 29 + // 29 28 29 28 29 29 29 29 29 29 29 29 29 + // 28 29 29 29 28 29 28 29 28 29 28 + // 28 29 28 29 28 29 28 29 28 29 + // 29 28 29 28 29 28 29 28 29 + // 29 28 28 29 29 29 29 29 29 + // 28 29 28 28 28 28 28 + // 28 29 28 29 28 29 + // 29 28 29 28 29 + // 29 28 29 28 29 + // 29 28 29 + // 29 + // ------------------------------------------------- + // according the table, from tmp2[6] to tmp[14], consider their initial value, + // they will overflow the word of 32bits, so we need to normalize them every iteration. + // This requires more CPU resources than NIST P256. + // + + tmp2[i+2] += (x << 7) & bottom29Bits + tmp2[i+3] += (x >> 22) + + // At position 86, which is the starting bit position for word 3, we + // have a factor of 0xffffc00 = 2**28 - 2**10 + tmp2[i+3] += 0x10000000 & xMask + tmp2[i+4] += (x - 1) & xMask + tmp2[i+3] -= (x << 10) & bottom28Bits + tmp2[i+4] -= x >> 18 + + tmp2[i+4] += 0x20000000 & xMask + tmp2[i+4] -= x + tmp2[i+5] += (x - 1) & xMask + + tmp2[i+5] += 0x10000000 & xMask + tmp2[i+5] -= x + tmp2[i+6] += (x - 1) & xMask + + tmp2[i+6] += 0x20000000 & xMask + tmp2[i+6] -= x + tmp2[i+7] += (x - 1) & xMask + + // At position 200, which is the starting bit position for word 7, we + // have a factor of 0xeffffff = 2**28 - 2**24 - 1 + tmp2[i+7] += 0x10000000 & xMask + tmp2[i+7] -= x + tmp2[i+8] += (x - 1) & xMask + tmp2[i+7] -= (x << 24) & bottom28Bits + tmp2[i+8] -= x >> 4 + + tmp2[i+8] += 0x20000000 & xMask + tmp2[i+8] -= x + tmp2[i+8] += (x << 28) & bottom29Bits + tmp2[i+9] += ((x >> 1) - 1) & xMask + + if i+1 == p256Limbs { + break + } + + tmp2[i+2] += tmp2[i+1] >> 28 + x = tmp2[i+1] & bottom28Bits + xMask = nonZeroToAllOnes(x) + tmp2[i+1] = 0 + + tmp2[i+3] += (x << 7) & bottom28Bits + tmp2[i+4] += (x >> 21) + + // At position 85, which is the starting bit position for word 3, we + // have a factor of 0x1ffff800 = 2**29 - 2**11 + tmp2[i+4] += 0x20000000 & xMask + tmp2[i+5] += (x - 1) & xMask + tmp2[i+4] -= (x << 11) & bottom29Bits + tmp2[i+5] -= x >> 18 + + tmp2[i+5] += 0x10000000 & xMask + tmp2[i+5] -= x + tmp2[i+6] += (x - 1) & xMask + + tmp2[i+6] += 0x20000000 & xMask + tmp2[i+6] -= x + tmp2[i+7] += (x - 1) & xMask + + tmp2[i+7] += 0x10000000 & xMask + tmp2[i+7] -= x + tmp2[i+8] += (x - 1) & xMask + + // At position 199, which is the starting bit position for word 7, we + // have a factor of 0x1dffffff = 2**29 - 2**25 - 1 + tmp2[i+8] += 0x20000000 & xMask + tmp2[i+8] -= x + tmp2[i+9] += (x - 1) & xMask + tmp2[i+8] -= (x << 25) & bottom29Bits + tmp2[i+9] -= x >> 4 + + tmp2[i+9] += 0x10000000 & xMask + tmp2[i+9] -= x + tmp2[i+10] += (x - 1) & xMask + + // Need to normalize below limbs to avoid overflow the word in the next iteration + tmp2[i+7] += tmp2[i+6] >> 29 + tmp2[i+6] = tmp2[i+6] & bottom29Bits + + tmp2[i+8] += tmp2[i+7] >> 28 + tmp2[i+7] = tmp2[i+7] & bottom28Bits + + tmp2[i+9] += tmp2[i+8] >> 29 + tmp2[i+8] = tmp2[i+8] & bottom29Bits + + tmp2[i+10] += tmp2[i+9] >> 28 + tmp2[i+9] = tmp2[i+9] & bottom28Bits + } + + // We merge the right shift with a carry chain. The words above 2**257 have + // widths of 28,29,... which we need to correct when copying them down. + carry = 0 + for i := 0; i < 8; i++ { + // The maximum value of tmp2[i + 9] occurs on the first iteration and + // is < 2**30+2**29+2**28. Adding 2**29 (from tmp2[i + 10]) is + // therefore safe. + out[i] = tmp2[i+9] + out[i] += carry + out[i] += (tmp2[i+10] << 28) & bottom29Bits + carry = out[i] >> 29 + out[i] &= bottom29Bits + + i++ + out[i] = tmp2[i+9] >> 1 + out[i] += carry + carry = out[i] >> 28 + out[i] &= bottom28Bits + } + + out[8] = tmp2[17] + out[8] += carry + carry = out[8] >> 29 + out[8] &= bottom29Bits + + p256ReduceCarry(out, carry) +} + +// p256Square sets out=in*in. +// +// On entry: in[0,2,...] < 2**30, in[1,3,...] < 2**29. +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +func p256Square(out, in *[p256Limbs]uint32) { + var tmp [17]uint64 + + tmp[0] = uint64(in[0]) * uint64(in[0]) + tmp[1] = uint64(in[0]) * (uint64(in[1]) << 1) + tmp[2] = uint64(in[0])*(uint64(in[2])<<1) + + uint64(in[1])*(uint64(in[1])<<1) + tmp[3] = uint64(in[0])*(uint64(in[3])<<1) + + uint64(in[1])*(uint64(in[2])<<1) + tmp[4] = uint64(in[0])*(uint64(in[4])<<1) + + uint64(in[1])*(uint64(in[3])<<2) + + uint64(in[2])*uint64(in[2]) + tmp[5] = uint64(in[0])*(uint64(in[5])<<1) + + uint64(in[1])*(uint64(in[4])<<1) + + uint64(in[2])*(uint64(in[3])<<1) + tmp[6] = uint64(in[0])*(uint64(in[6])<<1) + + uint64(in[1])*(uint64(in[5])<<2) + + uint64(in[2])*(uint64(in[4])<<1) + + uint64(in[3])*(uint64(in[3])<<1) + tmp[7] = uint64(in[0])*(uint64(in[7])<<1) + + uint64(in[1])*(uint64(in[6])<<1) + + uint64(in[2])*(uint64(in[5])<<1) + + uint64(in[3])*(uint64(in[4])<<1) + // tmp[8] has the greatest value of 2**61 + 2**60 + 2**61 + 2**60 + 2**60, + // which is < 2**64 as required. + tmp[8] = uint64(in[0])*(uint64(in[8])<<1) + + uint64(in[1])*(uint64(in[7])<<2) + + uint64(in[2])*(uint64(in[6])<<1) + + uint64(in[3])*(uint64(in[5])<<2) + + uint64(in[4])*uint64(in[4]) + tmp[9] = uint64(in[1])*(uint64(in[8])<<1) + + uint64(in[2])*(uint64(in[7])<<1) + + uint64(in[3])*(uint64(in[6])<<1) + + uint64(in[4])*(uint64(in[5])<<1) + tmp[10] = uint64(in[2])*(uint64(in[8])<<1) + + uint64(in[3])*(uint64(in[7])<<2) + + uint64(in[4])*(uint64(in[6])<<1) + + uint64(in[5])*(uint64(in[5])<<1) + tmp[11] = uint64(in[3])*(uint64(in[8])<<1) + + uint64(in[4])*(uint64(in[7])<<1) + + uint64(in[5])*(uint64(in[6])<<1) + tmp[12] = uint64(in[4])*(uint64(in[8])<<1) + + uint64(in[5])*(uint64(in[7])<<2) + + uint64(in[6])*uint64(in[6]) + tmp[13] = uint64(in[5])*(uint64(in[8])<<1) + + uint64(in[6])*(uint64(in[7])<<1) + tmp[14] = uint64(in[6])*(uint64(in[8])<<1) + + uint64(in[7])*(uint64(in[7])<<1) + tmp[15] = uint64(in[7]) * (uint64(in[8]) << 1) + tmp[16] = uint64(in[8]) * uint64(in[8]) + + p256ReduceDegree(out, tmp) +} + +// p256Mul sets out=in*in2. +// +// On entry: in[0,2,...] < 2**30, in[1,3,...] < 2**29 and +// in2[0,2,...] < 2**30, in2[1,3,...] < 2**29. +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +func p256Mul(out, in, in2 *[p256Limbs]uint32) { + var tmp [17]uint64 + + tmp[0] = uint64(in[0]) * uint64(in2[0]) + tmp[1] = uint64(in[0])*(uint64(in2[1])<<0) + //2**29 + uint64(in[1])*(uint64(in2[0])<<0) + tmp[2] = uint64(in[0])*(uint64(in2[2])<<0) + //2**57 + uint64(in[1])*(uint64(in2[1])<<1) + + uint64(in[2])*(uint64(in2[0])<<0) + tmp[3] = uint64(in[0])*(uint64(in2[3])<<0) + //2**86 + uint64(in[1])*(uint64(in2[2])<<0) + + uint64(in[2])*(uint64(in2[1])<<0) + + uint64(in[3])*(uint64(in2[0])<<0) + tmp[4] = uint64(in[0])*(uint64(in2[4])<<0) + //2**114 + uint64(in[1])*(uint64(in2[3])<<1) + + uint64(in[2])*(uint64(in2[2])<<0) + + uint64(in[3])*(uint64(in2[1])<<1) + + uint64(in[4])*(uint64(in2[0])<<0) + tmp[5] = uint64(in[0])*(uint64(in2[5])<<0) + //2**143 + uint64(in[1])*(uint64(in2[4])<<0) + + uint64(in[2])*(uint64(in2[3])<<0) + + uint64(in[3])*(uint64(in2[2])<<0) + + uint64(in[4])*(uint64(in2[1])<<0) + + uint64(in[5])*(uint64(in2[0])<<0) + tmp[6] = uint64(in[0])*(uint64(in2[6])<<0) + //2**171 + uint64(in[1])*(uint64(in2[5])<<1) + + uint64(in[2])*(uint64(in2[4])<<0) + + uint64(in[3])*(uint64(in2[3])<<1) + + uint64(in[4])*(uint64(in2[2])<<0) + + uint64(in[5])*(uint64(in2[1])<<1) + + uint64(in[6])*(uint64(in2[0])<<0) + tmp[7] = uint64(in[0])*(uint64(in2[7])<<0) + //2**200 + uint64(in[1])*(uint64(in2[6])<<0) + + uint64(in[2])*(uint64(in2[5])<<0) + + uint64(in[3])*(uint64(in2[4])<<0) + + uint64(in[4])*(uint64(in2[3])<<0) + + uint64(in[5])*(uint64(in2[2])<<0) + + uint64(in[6])*(uint64(in2[1])<<0) + + uint64(in[7])*(uint64(in2[0])<<0) + // tmp[8] has the greatest value but doesn't overflow. See logic in + // p256Square. + tmp[8] = uint64(in[0])*(uint64(in2[8])<<0) + // 2**228 + uint64(in[1])*(uint64(in2[7])<<1) + + uint64(in[2])*(uint64(in2[6])<<0) + + uint64(in[3])*(uint64(in2[5])<<1) + + uint64(in[4])*(uint64(in2[4])<<0) + + uint64(in[5])*(uint64(in2[3])<<1) + + uint64(in[6])*(uint64(in2[2])<<0) + + uint64(in[7])*(uint64(in2[1])<<1) + + uint64(in[8])*(uint64(in2[0])<<0) + tmp[9] = uint64(in[1])*(uint64(in2[8])<<0) + //2**257 + uint64(in[2])*(uint64(in2[7])<<0) + + uint64(in[3])*(uint64(in2[6])<<0) + + uint64(in[4])*(uint64(in2[5])<<0) + + uint64(in[5])*(uint64(in2[4])<<0) + + uint64(in[6])*(uint64(in2[3])<<0) + + uint64(in[7])*(uint64(in2[2])<<0) + + uint64(in[8])*(uint64(in2[1])<<0) + tmp[10] = uint64(in[2])*(uint64(in2[8])<<0) + //2**285 + uint64(in[3])*(uint64(in2[7])<<1) + + uint64(in[4])*(uint64(in2[6])<<0) + + uint64(in[5])*(uint64(in2[5])<<1) + + uint64(in[6])*(uint64(in2[4])<<0) + + uint64(in[7])*(uint64(in2[3])<<1) + + uint64(in[8])*(uint64(in2[2])<<0) + tmp[11] = uint64(in[3])*(uint64(in2[8])<<0) + //2**314 + uint64(in[4])*(uint64(in2[7])<<0) + + uint64(in[5])*(uint64(in2[6])<<0) + + uint64(in[6])*(uint64(in2[5])<<0) + + uint64(in[7])*(uint64(in2[4])<<0) + + uint64(in[8])*(uint64(in2[3])<<0) + tmp[12] = uint64(in[4])*(uint64(in2[8])<<0) + //2**342 + uint64(in[5])*(uint64(in2[7])<<1) + + uint64(in[6])*(uint64(in2[6])<<0) + + uint64(in[7])*(uint64(in2[5])<<1) + + uint64(in[8])*(uint64(in2[4])<<0) + tmp[13] = uint64(in[5])*(uint64(in2[8])<<0) + //2**371 + uint64(in[6])*(uint64(in2[7])<<0) + + uint64(in[7])*(uint64(in2[6])<<0) + + uint64(in[8])*(uint64(in2[5])<<0) + tmp[14] = uint64(in[6])*(uint64(in2[8])<<0) + //2**399 + uint64(in[7])*(uint64(in2[7])<<1) + + uint64(in[8])*(uint64(in2[6])<<0) + tmp[15] = uint64(in[7])*(uint64(in2[8])<<0) + //2**428 + uint64(in[8])*(uint64(in2[7])<<0) + tmp[16] = uint64(in[8]) * (uint64(in2[8]) << 0) //2**456 + + p256ReduceDegree(out, tmp) +} + +func p256Assign(out, in *[p256Limbs]uint32) { + *out = *in +} + +// p256Invert calculates |out| = |in|^{-1} +// +// Based on Fermat's Little Theorem: +// a^p = a (mod p) +// a^{p-1} = 1 (mod p) +// a^{p-2} = a^{-1} (mod p) +func p256Invert(out, in *[p256Limbs]uint32) { + var ftmp, ftmp2 [p256Limbs]uint32 + + // each e_I will hold |in|^{2^I - 1} + var e2, e4, e8, e16, e32, e64 [p256Limbs]uint32 + // 2^32-2 + var e32m2 [p256Limbs]uint32 + + p256Square(&ftmp, in) // 2^1 + p256Assign(&ftmp2, &ftmp) + p256Mul(&ftmp, in, &ftmp) // 2^2 - 2^0 + p256Assign(&e2, &ftmp) + p256Square(&ftmp, &ftmp) // 2^3 - 2^1 + p256Square(&ftmp, &ftmp) // 2^4 - 2^2 + p256Assign(&e32m2, &ftmp) + p256Mul(&e32m2, &e32m2, &ftmp2) // 2^4 - 2^2 + 2^1 = 2^4 - 2 + p256Mul(&ftmp, &ftmp, &e2) // 2^4 - 2^0 + p256Assign(&e4, &ftmp) + for i := 0; i < 4; i++ { + p256Square(&ftmp, &ftmp) + } // 2^8 - 2^4 + p256Mul(&e32m2, &e32m2, &ftmp) // 2^8 - 2 + + p256Mul(&ftmp, &ftmp, &e4) // 2^8 - 2^0 + p256Assign(&e8, &ftmp) + for i := 0; i < 8; i++ { + p256Square(&ftmp, &ftmp) + } // 2^16 - 2^8 + p256Mul(&e32m2, &e32m2, &ftmp) // 2^16 - 2 + p256Mul(&ftmp, &ftmp, &e8) // 2^16 - 2^0 + p256Assign(&e16, &ftmp) + for i := 0; i < 16; i++ { + p256Square(&ftmp, &ftmp) + } // 2^32 - 2^16 + p256Mul(&e32m2, &e32m2, &ftmp) // 2^32 - 2 + + p256Mul(&ftmp, &ftmp, &e16) // 2^32 - 2^0 + p256Assign(&e32, &ftmp) + for i := 0; i < 32; i++ { + p256Square(&ftmp, &ftmp) + } // 2^64 - 2^32 + p256Assign(&e64, &ftmp) + p256Mul(&e64, &e64, &e32) // 2^64 - 2^0 + p256Assign(&ftmp, &e64) + + for i := 0; i < 64; i++ { + p256Square(&ftmp, &ftmp) + } // 2^128 - 2^64 + p256Mul(&ftmp, &ftmp, &e64) // 2^128 - 1 + + for i := 0; i < 32; i++ { + p256Square(&ftmp, &ftmp) + } // 2^160 - 2^32 + + p256Mul(&ftmp, &ftmp, &e32m2) // 2^160 - 2 + + for i := 0; i < 95; i++ { + p256Square(&ftmp, &ftmp) + } // 2^255 - 2^96 + + p256Assign(&ftmp2, &e32m2) + for i := 0; i < 223; i++ { + p256Square(&ftmp2, &ftmp2) + } // 2^255 - 2^224 + + p256Mul(&ftmp, &ftmp, &ftmp2) // 2^256 - 2^224 - 2^96 + + p256Assign(&ftmp2, &e32) + + for i := 0; i < 16; i++ { + p256Square(&ftmp2, &ftmp2) + } // 2^48 - 2^16 + p256Mul(&ftmp2, &e16, &ftmp2) // 2^48 - 2^0 + + for i := 0; i < 8; i++ { + p256Square(&ftmp2, &ftmp2) + } // 2^56 - 2^8 + p256Mul(&ftmp2, &e8, &ftmp2) // 2^56 - 2^0 + + for i := 0; i < 4; i++ { + p256Square(&ftmp2, &ftmp2) + } // 2^60 - 2^4 + p256Mul(&ftmp2, &e4, &ftmp2) // 2^60 - 2^0 + + for i := 0; i < 2; i++ { + p256Square(&ftmp2, &ftmp2) + } // 2^62 - 2^2 + + p256Mul(&ftmp2, &e2, &ftmp2) // 2^62 - 2^0 + for i := 0; i < 2; i++ { + p256Square(&ftmp2, &ftmp2) + } // 2^64 - 2^2 + p256Mul(&ftmp2, in, &ftmp2) // 2^64 - 3 + p256Mul(out, &ftmp2, &ftmp) // 2^256 - 2^224 - 2^96 + 2^64 - 3 +} + +// p256Scalar3 sets out=3*out. +// +// On entry: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +func p256Scalar3(out *[p256Limbs]uint32) { + var carry uint32 + + for i := 0; ; i++ { + out[i] *= 3 + out[i] += carry + carry = out[i] >> 29 + out[i] &= bottom29Bits + + i++ + if i == p256Limbs { + break + } + + out[i] *= 3 + out[i] += carry + carry = out[i] >> 28 + out[i] &= bottom28Bits + } + + p256ReduceCarry(out, carry) +} + +// p256Scalar4 sets out=4*out. +// +// On entry: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +func p256Scalar4(out *[p256Limbs]uint32) { + var carry, nextCarry uint32 + + for i := 0; ; i++ { + nextCarry = out[i] >> 27 + out[i] <<= 2 + out[i] &= bottom29Bits + out[i] += carry + carry = nextCarry + (out[i] >> 29) + out[i] &= bottom29Bits + + i++ + if i == p256Limbs { + break + } + nextCarry = out[i] >> 26 + out[i] <<= 2 + out[i] &= bottom28Bits + out[i] += carry + carry = nextCarry + (out[i] >> 28) + out[i] &= bottom28Bits + } + + p256ReduceCarry(out, carry) +} + +// p256Scalar8 sets out=8*out. +// +// On entry: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +// On exit: out[0,2,...] < 2**30, out[1,3,...] < 2**29. +func p256Scalar8(out *[p256Limbs]uint32) { + var carry, nextCarry uint32 + + for i := 0; ; i++ { + nextCarry = out[i] >> 26 + out[i] <<= 3 + out[i] &= bottom29Bits + out[i] += carry + carry = nextCarry + (out[i] >> 29) + out[i] &= bottom29Bits + + i++ + if i == p256Limbs { + break + } + nextCarry = out[i] >> 25 + out[i] <<= 3 + out[i] &= bottom28Bits + out[i] += carry + carry = nextCarry + (out[i] >> 28) + out[i] &= bottom28Bits + } + + p256ReduceCarry(out, carry) +} + +// Group operations: +// +// Elements of the elliptic curve group are represented in Jacobian +// coordinates: (x, y, z). An affine point (x', y') is x'=x/z**2, y'=y/z**3 in +// Jacobian form. + +// p256PointDouble sets {xOut,yOut,zOut} = 2*{x,y,z}. +// +// See https://www.hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#doubling-dbl-2009-l +func p256PointDouble(xOut, yOut, zOut, x, y, z *[p256Limbs]uint32) { + var delta, gamma, alpha, beta, tmp, tmp2 [p256Limbs]uint32 + + p256Square(&delta, z) // delta = z^2 + p256Square(&gamma, y) // gamma = y^2 + p256Mul(&beta, x, &gamma) // beta = x * gamma = x * y^2 + + p256Sum(&tmp, x, &delta) // tmp = x + delta = x + z^2 + p256Diff(&tmp2, x, &delta) // tmp2 = x - delta = x - z^2 + p256Mul(&alpha, &tmp, &tmp2) // alpha = tmp * tmp2 = (x + z^2) * (x - z^2) = x^2 - z^4 + p256Scalar3(&alpha) // alpha = alpah * 3 = 3*(x^2 - z^4) + + p256Sum(&tmp, y, z) // tmp = y+z + p256Square(&tmp, &tmp) // tmp = (y+z)^2 + p256Diff(&tmp, &tmp, &gamma) // tmp = tmp - gamma = (y+z)^2 - y^2 + p256Diff(zOut, &tmp, &delta) // zOut = tmp - delta = (y+z)^2 - y^2 - z^2 + + p256Scalar4(&beta) // beta = beta * 4 = 4 * x * y^2 + p256Square(xOut, &alpha) // xOut = alpha ^ 2 = (3*(x^2 - z^4))^2 + p256Diff(xOut, xOut, &beta) // xOut = xOut - beta = (3*(x^2 - z^4))^2 - 4 * x * y^2 + p256Diff(xOut, xOut, &beta) // xOut = xOut - beta = (3*(x^2 - z^4))^2 - 8 * x * y^2 + + p256Diff(&tmp, &beta, xOut) // tmp = beta - xOut + p256Mul(&tmp, &alpha, &tmp) // tmp = 3*(x^2 - z^4) * (beta - xOut) + p256Square(&tmp2, &gamma) // tmp2 = gamma^2 = y^4 + p256Scalar8(&tmp2) // tmp2 = 8*tmp2 = 8*y^4 + p256Diff(yOut, &tmp, &tmp2) // yOut = (3*x^2 - 3*z^4) * (beta - xOut) - 8*y^4 +} + +// p256PointAddMixed sets {xOut,yOut,zOut} = {x1,y1,z1} + {x2,y2,1}. +// (i.e. the second point is affine.) +// +// See https://www.hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#addition-add-2007-bl +// +// Note that this function does not handle P+P, infinity+P nor P+infinity +// correctly. +func p256PointAddMixed(xOut, yOut, zOut, x1, y1, z1, x2, y2 *[p256Limbs]uint32) { + var z1z1, z1z1z1, s2, u2, h, i, j, r, rr, v, tmp [p256Limbs]uint32 + + p256Square(&z1z1, z1) + p256Sum(&tmp, z1, z1) + + p256Mul(&u2, x2, &z1z1) + p256Mul(&z1z1z1, z1, &z1z1) + p256Mul(&s2, y2, &z1z1z1) + p256Diff(&h, &u2, x1) + p256Sum(&i, &h, &h) + p256Square(&i, &i) + p256Mul(&j, &h, &i) + p256Diff(&r, &s2, y1) + p256Sum(&r, &r, &r) + p256Mul(&v, x1, &i) + + p256Mul(zOut, &tmp, &h) + p256Square(&rr, &r) + p256Diff(xOut, &rr, &j) + p256Diff(xOut, xOut, &v) + p256Diff(xOut, xOut, &v) + + p256Diff(&tmp, &v, xOut) + p256Mul(yOut, &tmp, &r) + p256Mul(&tmp, y1, &j) + p256Diff(yOut, yOut, &tmp) + p256Diff(yOut, yOut, &tmp) +} + +// p256PointAdd sets {xOut,yOut,zOut} = {x1,y1,z1} + {x2,y2,z2}. +// +// See https://www.hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-0.html#addition-add-2007-bl +// +// Note that this function does not handle P+P, infinity+P nor P+infinity +// correctly. +func p256PointAdd(xOut, yOut, zOut, x1, y1, z1, x2, y2, z2 *[p256Limbs]uint32) { + var z1z1, z1z1z1, z2z2, z2z2z2, s1, s2, u1, u2, h, i, j, r, rr, v, tmp [p256Limbs]uint32 + + p256Square(&z1z1, z1) + p256Square(&z2z2, z2) + p256Mul(&u1, x1, &z2z2) + + p256Sum(&tmp, z1, z2) + p256Square(&tmp, &tmp) + p256Diff(&tmp, &tmp, &z1z1) + p256Diff(&tmp, &tmp, &z2z2) + + p256Mul(&z2z2z2, z2, &z2z2) + p256Mul(&s1, y1, &z2z2z2) + + p256Mul(&u2, x2, &z1z1) + p256Mul(&z1z1z1, z1, &z1z1) + p256Mul(&s2, y2, &z1z1z1) + p256Diff(&h, &u2, &u1) + p256Sum(&i, &h, &h) + p256Square(&i, &i) + p256Mul(&j, &h, &i) + p256Diff(&r, &s2, &s1) + p256Sum(&r, &r, &r) + p256Mul(&v, &u1, &i) + + p256Mul(zOut, &tmp, &h) + p256Square(&rr, &r) + p256Diff(xOut, &rr, &j) + p256Diff(xOut, xOut, &v) + p256Diff(xOut, xOut, &v) + + p256Diff(&tmp, &v, xOut) + p256Mul(yOut, &tmp, &r) + p256Mul(&tmp, &s1, &j) + p256Diff(yOut, yOut, &tmp) + p256Diff(yOut, yOut, &tmp) +} + +// p256CopyConditional sets out=in if mask = 0xffffffff in constant time. +// +// On entry: mask is either 0 or 0xffffffff. +func p256CopyConditional(out, in *[p256Limbs]uint32, mask uint32) { + for i := 0; i < p256Limbs; i++ { + tmp := mask & (in[i] ^ out[i]) + out[i] ^= tmp + } +} + +// p256SelectAffinePoint sets {out_x,out_y} to the index'th entry of table. +// On entry: index < 16, table[0] must be zero. +func p256SelectAffinePoint(xOut, yOut *[p256Limbs]uint32, table []uint32, index uint32) { + for i := range xOut { + xOut[i] = 0 + } + for i := range yOut { + yOut[i] = 0 + } + + for i := uint32(1); i < 16; i++ { + mask := i ^ index + mask |= mask >> 2 + mask |= mask >> 1 + mask &= 1 + mask-- + for j := range xOut { + xOut[j] |= table[0] & mask + table = table[1:] + } + for j := range yOut { + yOut[j] |= table[0] & mask + table = table[1:] + } + } +} + +// p256SelectJacobianPoint sets {out_x,out_y,out_z} to the index'th entry of +// table. +// On entry: index < 16, table[0] must be zero. +func p256SelectJacobianPoint(xOut, yOut, zOut *[p256Limbs]uint32, table *[16][3][p256Limbs]uint32, index uint32) { + for i := range xOut { + xOut[i] = 0 + } + for i := range yOut { + yOut[i] = 0 + } + for i := range zOut { + zOut[i] = 0 + } + + // The implicit value at index 0 is all zero. We don't need to perform that + // iteration of the loop because we already set out_* to zero. + for i := uint32(1); i < 16; i++ { + mask := i ^ index + mask |= mask >> 2 + mask |= mask >> 1 + mask &= 1 + mask-- + for j := range xOut { + xOut[j] |= table[i][0][j] & mask + } + for j := range yOut { + yOut[j] |= table[i][1][j] & mask + } + for j := range zOut { + zOut[j] |= table[i][2][j] & mask + } + } +} + +// p256GetBit returns the bit'th bit of scalar. +func p256GetBit(scalar *[32]uint8, bit uint) uint32 { + return uint32(((scalar[bit>>3]) >> (bit & 7)) & 1) +} + +// p256ScalarBaseMult sets {xOut,yOut,zOut} = scalar*G where scalar is a +// little-endian number. Note that the value of scalar must be less than the +// order of the group. +func p256ScalarBaseMult(xOut, yOut, zOut *[p256Limbs]uint32, scalar *[32]uint8) { + nIsInfinityMask := ^uint32(0) + var pIsNoninfiniteMask, mask, tableOffset uint32 + var px, py, tx, ty, tz [p256Limbs]uint32 + + for i := range xOut { + xOut[i] = 0 + } + for i := range yOut { + yOut[i] = 0 + } + for i := range zOut { + zOut[i] = 0 + } + + // The loop adds bits at positions 0, 64, 128 and 192, followed by + // positions 32,96,160 and 224 and does this 32 times. + for i := uint(0); i < 32; i++ { + if i != 0 { + p256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut) + } + tableOffset = 0 + for j := uint(0); j <= 32; j += 32 { + bit0 := p256GetBit(scalar, 31-i+j) + bit1 := p256GetBit(scalar, 95-i+j) + bit2 := p256GetBit(scalar, 159-i+j) + bit3 := p256GetBit(scalar, 223-i+j) + index := bit0 | (bit1 << 1) | (bit2 << 2) | (bit3 << 3) + + p256SelectAffinePoint(&px, &py, p256Precomputed[tableOffset:], index) + tableOffset += 30 * p256Limbs + + // Since scalar is less than the order of the group, we know that + // {xOut,yOut,zOut} != {px,py,1}, unless both are zero, which we handle + // below. + p256PointAddMixed(&tx, &ty, &tz, xOut, yOut, zOut, &px, &py) + // The result of pointAddMixed is incorrect if {xOut,yOut,zOut} is zero + // (a.k.a. the point at infinity). We handle that situation by + // copying the point from the table. + p256CopyConditional(xOut, &px, nIsInfinityMask) + p256CopyConditional(yOut, &py, nIsInfinityMask) + p256CopyConditional(zOut, &p256One, nIsInfinityMask) + + // Equally, the result is also wrong if the point from the table is + // zero, which happens when the index is zero. We handle that by + // only copying from {tx,ty,tz} to {xOut,yOut,zOut} if index != 0. + pIsNoninfiniteMask = nonZeroToAllOnes(index) + mask = pIsNoninfiniteMask & ^nIsInfinityMask + p256CopyConditional(xOut, &tx, mask) + p256CopyConditional(yOut, &ty, mask) + p256CopyConditional(zOut, &tz, mask) + // If p was not zero, then n is now non-zero. + nIsInfinityMask &^= pIsNoninfiniteMask + } + } +} + +// p256PointToAffine converts a Jacobian point to an affine point. If the input +// is the point at infinity then it returns (0, 0) in constant time. +func p256PointToAffine(xOut, yOut, x, y, z *[p256Limbs]uint32) { + var zInv, zInvSq [p256Limbs]uint32 + + p256Invert(&zInv, z) + p256Square(&zInvSq, &zInv) + p256Mul(xOut, x, &zInvSq) + p256Mul(&zInv, &zInv, &zInvSq) + p256Mul(yOut, y, &zInv) +} + +// p256ToAffine returns a pair of *big.Int containing the affine representation +// of {x,y,z}. +func p256ToAffine(x, y, z *[p256Limbs]uint32) (xOut, yOut *big.Int) { + var xx, yy [p256Limbs]uint32 + p256PointToAffine(&xx, &yy, x, y, z) + return p256ToBig(&xx), p256ToBig(&yy) +} + +// p256ScalarMult sets {xOut,yOut,zOut} = scalar*{x,y}. +func p256ScalarMult(xOut, yOut, zOut, x, y *[p256Limbs]uint32, scalar *[32]uint8) { + var px, py, pz, tx, ty, tz [p256Limbs]uint32 + var precomp [16][3][p256Limbs]uint32 + var nIsInfinityMask, index, pIsNoninfiniteMask, mask uint32 + + // We precompute 0,1,2,... times {x,y}. + precomp[1][0] = *x + precomp[1][1] = *y + precomp[1][2] = p256One + + for i := 2; i < 16; i += 2 { + p256PointDouble(&precomp[i][0], &precomp[i][1], &precomp[i][2], &precomp[i/2][0], &precomp[i/2][1], &precomp[i/2][2]) + p256PointAddMixed(&precomp[i+1][0], &precomp[i+1][1], &precomp[i+1][2], &precomp[i][0], &precomp[i][1], &precomp[i][2], x, y) + } + + for i := range xOut { + xOut[i] = 0 + } + for i := range yOut { + yOut[i] = 0 + } + for i := range zOut { + zOut[i] = 0 + } + nIsInfinityMask = ^uint32(0) + + // We add in a window of four bits each iteration and do this 64 times. + for i := 0; i < 64; i++ { + if i != 0 { + p256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut) + p256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut) + p256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut) + p256PointDouble(xOut, yOut, zOut, xOut, yOut, zOut) + } + + index = uint32(scalar[31-i/2]) + if (i & 1) == 1 { + index &= 15 + } else { + index >>= 4 + } + + // See the comments in scalarBaseMult about handling infinities. + p256SelectJacobianPoint(&px, &py, &pz, &precomp, index) + p256PointAdd(&tx, &ty, &tz, xOut, yOut, zOut, &px, &py, &pz) + p256CopyConditional(xOut, &px, nIsInfinityMask) + p256CopyConditional(yOut, &py, nIsInfinityMask) + p256CopyConditional(zOut, &pz, nIsInfinityMask) + + pIsNoninfiniteMask = nonZeroToAllOnes(index) + mask = pIsNoninfiniteMask & ^nIsInfinityMask + p256CopyConditional(xOut, &tx, mask) + p256CopyConditional(yOut, &ty, mask) + p256CopyConditional(zOut, &tz, mask) + nIsInfinityMask &^= pIsNoninfiniteMask + } +} + +// p256FromBig sets out = R*in. +func p256FromBig(out *[p256Limbs]uint32, in *big.Int) { + p256FromBigAgainstP(out, in, p256.P) +} + +func p256FromBigAgainstP(out *[p256Limbs]uint32, in *big.Int, p *big.Int) { + tmp := new(big.Int).Lsh(in, 257) + tmp.Mod(tmp, p) + + for i := 0; i < p256Limbs; i++ { + if bits := tmp.Bits(); len(bits) > 0 { + out[i] = uint32(bits[0]) & bottom29Bits + } else { + out[i] = 0 + } + tmp.Rsh(tmp, 29) + + i++ + if i == p256Limbs { + break + } + + if bits := tmp.Bits(); len(bits) > 0 { + out[i] = uint32(bits[0]) & bottom28Bits + } else { + out[i] = 0 + } + tmp.Rsh(tmp, 28) + } +} + +// p256ToBig returns a *big.Int containing the value of in. +func p256ToBig(in *[p256Limbs]uint32) *big.Int { + result := limbsToBig(in) + result.Mul(result, p256RInverse) + result.Mod(result, p256.P) + return result +} diff --git a/sm2/sm2_test.go b/sm2/sm2_test.go index 20b43f1..eafa350 100644 --- a/sm2/sm2_test.go +++ b/sm2/sm2_test.go @@ -2,6 +2,7 @@ package sm2 import ( "crypto/ecdsa" + "crypto/elliptic" "crypto/rand" "encoding/hex" "math/big" @@ -55,17 +56,25 @@ func Test_encryptDecrypt(t *testing.T) { } } -func benchmarkEncrypt(b *testing.B, plaintext string) { +func benchmarkEncrypt(b *testing.B, curve elliptic.Curve, plaintext string) { for i := 0; i < b.N; i++ { - priv, _ := ecdsa.GenerateKey(P256(), rand.Reader) + priv, _ := ecdsa.GenerateKey(curve, rand.Reader) Encrypt(rand.Reader, &priv.PublicKey, []byte(plaintext)) } } -func BenchmarkLessThan32(b *testing.B) { - benchmarkEncrypt(b, "encryption standard") +func BenchmarkLessThan32_P256(b *testing.B) { + benchmarkEncrypt(b, elliptic.P256(), "encryption standard") } -func BenchmarkMoreThan32(b *testing.B) { - benchmarkEncrypt(b, "encryption standard encryption standard encryption standard encryption standard encryption standard encryption standard encryption standard") +func BenchmarkLessThan32_P256SM2(b *testing.B) { + benchmarkEncrypt(b, P256(), "encryption standard") +} + +func BenchmarkMoreThan32_P256(b *testing.B) { + benchmarkEncrypt(b, elliptic.P256(), "encryption standard encryption standard encryption standard encryption standard encryption standard encryption standard encryption standard") +} + +func BenchmarkMoreThan32_P256SM2(b *testing.B) { + benchmarkEncrypt(b, P256(), "encryption standard encryption standard encryption standard encryption standard encryption standard encryption standard encryption standard") } diff --git a/sm2/util.go b/sm2/util.go index 4fc0291..4a8de1a 100644 --- a/sm2/util.go +++ b/sm2/util.go @@ -8,7 +8,7 @@ import ( "strings" ) -var zero = new(big.Int).SetInt64(0) +var zero = big.NewInt(0) func toBytes(curve elliptic.Curve, value *big.Int) []byte { bytes := value.Bytes() @@ -97,7 +97,7 @@ func bytes2Point(curve elliptic.Curve, bytes []byte) (*big.Int, *big.Int, int, e return nil, nil, 0, fmt.Errorf("invalid compressed bytes length %d", len(bytes)) } if strings.HasPrefix(curve.Params().Name, "P-") { - // y² = x³ - 3x + b + // y² = x³ - 3x + b, prime curves x := toPointXY(bytes[1 : 1+byteLen]) y, err := calculatePrimeCurveY(curve, x) if err != nil {