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69 lines
1.7 KiB
Go
69 lines
1.7 KiB
Go
package ratchet
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import (
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"crypto/hmac"
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"crypto/sha256"
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)
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var messageKeySeed = []byte{0x01}
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var chainKeySeed = []byte{0x02}
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// NewSenderChainKey will return a new SenderChainKey.
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func NewSenderChainKey(iteration uint32, chainKey []byte) *SenderChainKey {
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return &SenderChainKey{
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iteration: iteration,
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chainKey: chainKey,
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}
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}
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// NewSenderChainKeyFromStruct will return a new chain key object from the
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// given serializeable structure.
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func NewSenderChainKeyFromStruct(structure *SenderChainKeyStructure) *SenderChainKey {
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return &SenderChainKey{
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iteration: structure.Iteration,
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chainKey: structure.ChainKey,
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}
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}
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// NewStructFromSenderChainKeys returns a serializeable structure of chain keys.
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func NewStructFromSenderChainKey(key *SenderChainKey) *SenderChainKeyStructure {
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return &SenderChainKeyStructure{
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Iteration: key.iteration,
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ChainKey: key.chainKey,
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}
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}
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// SenderChainKeyStructure is a serializeable structure of SenderChainKeys.
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type SenderChainKeyStructure struct {
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Iteration uint32
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ChainKey []byte
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}
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type SenderChainKey struct {
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iteration uint32
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chainKey []byte
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}
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func (k *SenderChainKey) Iteration() uint32 {
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return k.iteration
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}
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func (k *SenderChainKey) SenderMessageKey() (*SenderMessageKey, error) {
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return NewSenderMessageKey(k.iteration, k.getDerivative(messageKeySeed, k.chainKey))
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}
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func (k *SenderChainKey) Next() *SenderChainKey {
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return NewSenderChainKey(k.iteration+1, k.getDerivative(chainKeySeed, k.chainKey))
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}
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func (k *SenderChainKey) Seed() []byte {
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return k.chainKey
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}
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func (k *SenderChainKey) getDerivative(seed []byte, key []byte) []byte {
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mac := hmac.New(sha256.New, key[:])
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mac.Write(seed)
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return mac.Sum(nil)
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}
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