1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
package ratchet
import (
"crypto/hmac"
"crypto/sha256"
)
var messageKeySeed = []byte{0x01}
var chainKeySeed = []byte{0x02}
// NewSenderChainKey will return a new SenderChainKey.
func NewSenderChainKey(iteration uint32, chainKey []byte) *SenderChainKey {
return &SenderChainKey{
iteration: iteration,
chainKey: chainKey,
}
}
// NewSenderChainKeyFromStruct will return a new chain key object from the
// given serializeable structure.
func NewSenderChainKeyFromStruct(structure *SenderChainKeyStructure) *SenderChainKey {
return &SenderChainKey{
iteration: structure.Iteration,
chainKey: structure.ChainKey,
}
}
// NewStructFromSenderChainKeys returns a serializeable structure of chain keys.
func NewStructFromSenderChainKey(key *SenderChainKey) *SenderChainKeyStructure {
return &SenderChainKeyStructure{
Iteration: key.iteration,
ChainKey: key.chainKey,
}
}
// SenderChainKeyStructure is a serializeable structure of SenderChainKeys.
type SenderChainKeyStructure struct {
Iteration uint32
ChainKey []byte
}
type SenderChainKey struct {
iteration uint32
chainKey []byte
}
func (k *SenderChainKey) Iteration() uint32 {
return k.iteration
}
func (k *SenderChainKey) SenderMessageKey() (*SenderMessageKey, error) {
return NewSenderMessageKey(k.iteration, k.getDerivative(messageKeySeed, k.chainKey))
}
func (k *SenderChainKey) Next() *SenderChainKey {
return NewSenderChainKey(k.iteration+1, k.getDerivative(chainKeySeed, k.chainKey))
}
func (k *SenderChainKey) Seed() []byte {
return k.chainKey
}
func (k *SenderChainKey) getDerivative(seed []byte, key []byte) []byte {
mac := hmac.New(sha256.New, key[:])
mac.Write(seed)
return mac.Sum(nil)
}
|
