mirror of https://github.com/ethereum/go-ethereum
thanks to Felix Lange (fjl) for help with design & implpull/1862/head
Gustav Simonsson
9 years ago
parent
27a50c8f4b
commit
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// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package secp256k1 |
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import ( |
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"bytes" |
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"encoding/hex" |
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"math/big" |
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"testing" |
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) |
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func TestReadBits(t *testing.T) { |
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check := func(input string) { |
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want, _ := hex.DecodeString(input) |
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int, _ := new(big.Int).SetString(input, 16) |
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buf := make([]byte, len(want)) |
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readBits(buf, int) |
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if !bytes.Equal(buf, want) { |
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t.Errorf("have: %x\nwant: %x", buf, want) |
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} |
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} |
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check("000000000000000000000000000000000000000000000000000000FEFCF3F8F0") |
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check("0000000000012345000000000000000000000000000000000000FEFCF3F8F0") |
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check("18F8F8F1000111000110011100222004330052300000000000000000FEFCF3F8F0") |
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} |
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@ -0,0 +1,56 @@ |
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// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
|
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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/** Multiply point by scalar in constant time.
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* Returns: 1: multiplication was successful |
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* 0: scalar was invalid (zero or overflow) |
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* Args: ctx: pointer to a context object (cannot be NULL) |
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* Out: point: the multiplied point (usually secret) |
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* In: point: pointer to a 64-byte bytepublic point, |
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encoded as two 256bit big-endian numbers. |
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* scalar: a 32-byte scalar with which to multiply the point |
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*/ |
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int secp256k1_pubkey_scalar_mul(const secp256k1_context* ctx, unsigned char *point, const unsigned char *scalar) { |
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int ret = 0; |
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int overflow = 0; |
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secp256k1_fe feX, feY; |
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secp256k1_gej res; |
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secp256k1_ge ge; |
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secp256k1_scalar s; |
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ARG_CHECK(point != NULL); |
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ARG_CHECK(scalar != NULL); |
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(void)ctx; |
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secp256k1_fe_set_b32(&feX, point); |
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secp256k1_fe_set_b32(&feY, point+32); |
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secp256k1_ge_set_xy(&ge, &feX, &feY); |
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secp256k1_scalar_set_b32(&s, scalar, &overflow); |
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if (overflow || secp256k1_scalar_is_zero(&s)) { |
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ret = 0; |
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} else { |
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secp256k1_ecmult_const(&res, &ge, &s); |
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secp256k1_ge_set_gej(&ge, &res); |
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/* Note: can't use secp256k1_pubkey_save here because it is not constant time. */ |
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secp256k1_fe_normalize(&ge.x); |
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secp256k1_fe_normalize(&ge.y); |
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secp256k1_fe_get_b32(point, &ge.x); |
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secp256k1_fe_get_b32(point+32, &ge.y); |
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ret = 1; |
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} |
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secp256k1_scalar_clear(&s); |
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return ret; |
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} |
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