mirror of
https://source.quilibrium.com/quilibrium/ceremonyclient.git
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78 lines
2.1 KiB
Go
78 lines
2.1 KiB
Go
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//
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// Copyright Coinbase, Inc. All Rights Reserved.
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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package bbs
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import (
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"errors"
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"source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/core/curves"
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)
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// MessageGenerators are used to sign a vector of commitments for
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// a BBS+ signature. These must be the same generators used by
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// sign, verify, prove, and open
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//
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// These are generated in a deterministic manner. By using
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// MessageGenerators in this way, the generators do not need to be
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// stored alongside the public key and the same key can be used to sign
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// an arbitrary number of messages
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// Generators are created by computing
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// H_i = H_G1(W || I2OSP(0, 4) || I2OSP(0, 1) || I2OSP(length, 4))
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// where I2OSP means Integer to Octet Stream Primitive and
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// I2OSP represents an integer in a statically sized byte array.
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// `W` is the BBS+ public key.
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// Internally we store the 201 byte state since the only value that changes
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// is the index
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type MessageGenerators struct {
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// Blinding factor generator, stored, so we know what points to return in `Get`
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h0 curves.PairingPoint
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length int
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state [201]byte
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}
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// Init set the message generators to the default state
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func (msgg *MessageGenerators) Init(w *PublicKey, length int) (*MessageGenerators, error) {
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if length < 0 {
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return nil, errors.New("length should be nonnegative")
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}
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msgg.length = length
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for i := range msgg.state {
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msgg.state[i] = 0
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}
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copy(msgg.state[:192], w.value.ToAffineUncompressed())
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msgg.state[197] = byte(length >> 24)
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msgg.state[198] = byte(length >> 16)
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msgg.state[199] = byte(length >> 8)
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msgg.state[200] = byte(length)
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var ok bool
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msgg.h0, ok = w.value.OtherGroup().Hash(msgg.state[:]).(curves.PairingPoint)
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if !ok {
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return nil, errors.New("incorrect type conversion")
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}
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return msgg, nil
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}
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func (msgg MessageGenerators) Get(i int) curves.PairingPoint {
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if i <= 0 {
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return msgg.h0
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}
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if i > msgg.length {
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return nil
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}
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state := msgg.state
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state[193] = byte(i >> 24)
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state[194] = byte(i >> 16)
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state[195] = byte(i >> 8)
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state[196] = byte(i)
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point, ok := msgg.h0.Hash(msgg.state[:]).(curves.PairingPoint)
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if !ok {
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return nil
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}
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return point
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}
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