// VerifySignature verifies a signature header. It checks if the version, signatures and hashcash are correct.
func VerifySignature(header [SignHeaderSize]byte, minbits byte) (details *SignatureDetails, err error) {
var ok bool
if header[0] != byte(Version) {
return nil, ErrBadVersion
}
sd := new(SignatureDetails)
copy(sd.MsgID[:], header[signHeaderMsgIDStart:signHeaderMsgIDEnd])
copy(sd.PublicKey[:], header[signHeaderPubkeyStart:signHeaderPubkeyEnd])
copy(sd.HashCashNonce[:], header[signHeaderNonceStart:signHeaderNonceEnd])
signature := new([ed25519.SignatureSize]byte)
copy(signature[:], header[signHeaderSignatureStart:signHeaderSignatureEnd])
ok, sd.HashCashBits = hashcash.TestNonce(sd.PublicKey[:], sd.HashCashNonce[:], minbits)
if !ok {
return sd, ErrHashCash
}
ok = ed25519.Verify(&sd.PublicKey, sd.MsgID[:], signature)
if !ok {
return nil, ErrBadSignature
}
return sd, nil
}
// encrypt message.
func (sender *Sender) encrypt(messageType byte, message []byte, repost bool) (encMessage []byte, meta *MetaDataSend, err error) {
var Signer *SignKeyPair
meta = new(MetaDataSend)
// Set defaults
if sender.HashCashBits <= 0 {
sender.HashCashBits = DefaultHashCashBits
}
if sender.TotalLength <= 0 {
sender.TotalLength = DefaultTotalLength
}
if sender.PadToLength <= 0 {
sender.PadToLength = DefaultPadToLength
}
// Get signer
Signer = sender.Signer
// Verify if (optional) signer produces enough bits, if not, generate a new one
if Signer != nil {
ok, _ := hashcash.TestNonce(Signer.PublicKey[:], Signer.Nonce[:], sender.HashCashBits)
if !ok {
log.Debugf("Given signer does not produce enough HashCash bits: %x", Signer.PublicKey)
Signer = nil
}
}
if Signer == nil {
// We have no signer, so we generate one. Don't make public for sender instance
log.Info("Generating new HashCash signer...")
Signer, err = GenKey(sender.HashCashBits)
if err != nil {
return nil, nil, err
}
log.Info("...new HashCash signer generated")
}
// Generate sender keypack. if SenderPrivateKey is set, it will be used
keypackSender, err := GenSenderKeys(sender.SenderPrivateKey)
if err != nil {
return nil, nil, err
}
// Generate peer's keypack. If keys are known, they are used
keypackPeer, err := GenReceiveKeys(sender.ReceiveConstantPublicKey, sender.ReceiveTemporaryPublicKey)
if err != nil {
return nil, nil, err
}
// We generated new keys, they have to be made available
if sender.ReceiveConstantPublicKey == nil {
log.Debug("Using one-time receiver key")
meta.MessageKey = keypackPeer.ConstantPrivKey // TemporaryPrivKey is deterministic
}
// Generate the nonce
nonce, err := GenNonce()
if err != nil {
return nil, nil, err
}
myMessage := new(Message)
// Create our KeyHeader
myMessage.Header = PackKeyHeader(keypackSender, keypackPeer, nonce)
// Calculate our shared secret. We are the sender, so last param is true
sharedSecret := CalcSharedSecret(keypackSender, keypackPeer, nonce, true)
// Set encryption/padding parameters
bodyEncryption := EncryptBodyDef{
IV: *GenIV(myMessage.Header[:]), // Generate IV from key header, which is uniqueish
SharedSecret: sharedSecret,
MessageType: messageType,
TotalLength: sender.TotalLength - SignHeaderSize - KeyHeaderSize,
PadToLength: sender.PadToLength,
}
log.Debug("Encrypting...")
body, err := bodyEncryption.EncryptBody(message)
if err != nil {
return nil, nil, err
}
log.Debug("...encryption done")
// Convert body to bytes
myMessage.Body = body.Bytes()
// Generate the message ID. This has to happen the same way for repost and standard message
meta.MessageID = *myMessage.CalcMessageID()
meta.ReceiverConstantPubKey = keypackPeer.ConstantPubKey
myMessage.SignatureHeader = Signer.Sign(meta.MessageID)
if repost {
log.Debug("This is a repost-message!")
// Cut out padding and set padkey
meta.PadKey = &body.PadKey
myMessage.Body = body.BytesNoPadding()
// Repost messages are not base64 encoded since they are embedded anyways
return myMessage.Bytes(), meta, nil
}
return EncodeBase64(myMessage.Bytes()), meta, nil
}
func main() {
flag.Parse()
if *contCalc && *outFile != "" {
// Read token
d, err := utils.MaxReadFile(2048, *outFile)
if err != nil {
fmt.Printf("%s\n", err)
os.Exit(1)
}
kpt := new(message.SignKeyPair)
kp, err := kpt.Unmarshal(d)
if err != nil {
fmt.Printf("%s\n", err)
os.Exit(1)
}
fmt.Print("Continue")
start := hashcash.NonceToUInt64(kp.Nonce[:])
_, startBits := hashcash.TestNonce(kp.PublicKey[:], kp.Nonce[:], 0)
if len(d) == (ed25519.PublicKeySize + ed25519.PrivateKeySize + hashcash.NonceSize + 1 + 8) {
fmt.Print(" from state ")
start = hashcash.NonceToUInt64(d[ed25519.PublicKeySize+ed25519.PrivateKeySize+hashcash.NonceSize+1 : ed25519.PublicKeySize+ed25519.PrivateKeySize+hashcash.NonceSize+1+8])
}
fmt.Printf(" (%d, bits: %d) ", start, startBits)
for {
startBits++
nonce, _ := hashcash.ComputeNonceSelect(kp.PublicKey[:], startBits, start, start+hashcash.Steps*8)
start = hashcash.NonceToUInt64(nonce[:])
_, nextBits := hashcash.TestNonce(kp.PublicKey[:], nonce, 0)
if nextBits > startBits {
fmt.Printf("(%d)", nextBits)
copy(kp.Nonce[:], nonce)
kp.Bits = nextBits
startBits = nextBits
}
fmt.Print(".")
newData := append(kp.Marshal(), nonce[:]...)
err := utils.OverWriteFile(*outFile, newData)
if err != nil {
fmt.Printf("%s\n", err)
os.Exit(1)
}
if nextBits > byte(*minbits) {
fmt.Printf("\n%d reached. Finish.\n", nextBits)
os.Exit(0)
}
}
} else if *outDir == "" {
keypair, err := message.GenKey(byte(*minbits))
if err != nil {
fmt.Printf("%s\n", err)
os.Exit(1)
}
b := keypair.Marshal()
if *outFile != "" {
err := utils.WriteNewFile(*outFile, b)
if err != nil {
fmt.Printf("%s\n", err)
os.Exit(1)
}
} else {
os.Stdout.Write(b)
os.Stdout.Sync()
os.Exit(0)
}
} else {
for {
keypair, err := message.GenKey(byte(*minbits))
if err != nil {
fmt.Printf("%s\n", err)
os.Exit(1)
}
b := keypair.Marshal()
err = utils.WriteNewFile(*outDir+string(os.PathSeparator)+strconv.Itoa(int(time.Now().Unix()))+strconv.Itoa(int(time.Now().Nanosecond()))+".hashcash", b)
if err != nil {
fmt.Printf("%s\n", err)
os.Exit(1)
}
}
}
}