ceremonyclient/nekryptology/pkg/signatures/common/hmacdrbg.go
2023-07-05 00:32:28 -05:00

100 lines
1.8 KiB
Go

//
// Copyright Coinbase, Inc. All Rights Reserved.
//
// SPDX-License-Identifier: Apache-2.0
//
package common
import (
"crypto/hmac"
"hash"
)
// HmacDrbg is an HMAC deterministic random bit generator
// that can use any hash function. Handles reseeding
// automatically
type HmacDrbg struct {
k, v []byte
count int
hasher func() hash.Hash
}
func NewHmacDrbg(entropy, nonce, pers []byte, hasher func() hash.Hash) *HmacDrbg {
drbg := new(HmacDrbg)
h := hasher()
drbg.k = make([]byte, h.Size())
drbg.v = make([]byte, h.Size())
drbg.count = 0
drbg.hasher = hasher
for i := range drbg.v {
drbg.v[i] = 1
}
drbg.update([][]byte{entropy, nonce, pers})
drbg.count += 1
return drbg
}
func (drbg *HmacDrbg) Read(dst []byte) (n int, err error) {
toRead := len(dst)
if toRead == 0 {
return 0, nil
}
i := 0
for i < toRead {
vmac := drbg.getHmac()
_, _ = vmac.Write(drbg.v)
drbg.v = vmac.Sum(nil)
for j, b := range drbg.v {
dst[i+j] = b
}
i += len(drbg.v)
}
drbg.update(nil)
drbg.count++
return i, nil
}
func (drbg *HmacDrbg) Reseed(entropy []byte) {
drbg.update([][]byte{entropy})
}
func (drbg *HmacDrbg) getHmac() hash.Hash {
return hmac.New(drbg.hasher, drbg.k)
}
func (drbg *HmacDrbg) update(seeds [][]byte) {
kmac := drbg.getHmac()
_, _ = kmac.Write(drbg.v)
_, _ = kmac.Write([]byte{0})
if len(seeds) > 0 {
for _, seed := range seeds {
_, _ = kmac.Write(seed)
}
}
drbg.k = kmac.Sum(nil)
vmac := drbg.getHmac()
_, _ = vmac.Write(drbg.v)
drbg.v = vmac.Sum(nil)
if len(seeds) == 0 {
return
}
kmac = drbg.getHmac()
_, _ = kmac.Write(drbg.v)
_, _ = kmac.Write([]byte{1})
for _, seed := range seeds {
_, _ = kmac.Write(seed)
}
drbg.k = kmac.Sum(nil)
vmac = drbg.getHmac()
_, _ = vmac.Write(drbg.v)
drbg.v = vmac.Sum(nil)
}