// Generate a new stealth address
func new_stealth_address(prv_key []byte) {
sk, er := hex.DecodeString(*scankey)
if er != nil {
println(er.Error())
os.Exit(1)
}
if len(sk) != 33 || sk[0] != 2 && sk[0] != 3 {
println("scankey must be a compressed public key (33 bytes long)")
os.Exit(1)
}
if *prefix > 16 {
if *prefix > 24 {
fmt.Println("The stealth prefix cannot be bigger than 32", *prefix)
os.Exit(1)
}
fmt.Println("WARNING: You chose a prifix length of", *prefix)
fmt.Println("WARNING: Big prefixes endanger your anonymity.")
}
pub := btc.PublicFromPrivate(prv_key, true)
if pub == nil {
println("PublicFromPrivate error 2")
os.Exit(1)
}
sa := new(btc.StealthAddr)
sa.Version = btc.StealthAddressVersion(*testnet)
sa.Options = 0
copy(sa.ScanKey[:], sk)
sa.SpendKeys = make([][33]byte, 1)
copy(sa.SpendKeys[0][:], pub)
sa.Sigs = 1
sa.Prefix = make([]byte, 1+(byte(*prefix)+7)>>3)
if *prefix > 0 {
sa.Prefix[0] = byte(*prefix)
rand.Read(sa.Prefix[1:])
}
fmt.Println(sa.String())
}
// Thanks @dabura667 - https://bitcointalk.org/index.php?topic=590349.msg6560332#msg6560332
func stealth_txout(sa *btc.StealthAddr, value uint64) (res []*btc.TxOut) {
if sa.Version != btc.StealthAddressVersion(*testnet) {
fmt.Println("ERROR: Unsupported version of a stealth address", sa.Version)
os.Exit(1)
}
if len(sa.SpendKeys) != 1 {
fmt.Println("ERROR: Currently only non-multisig stealth addresses are supported",
len(sa.SpendKeys))
os.Exit(1)
}
// Make two outpus
res = make([]*btc.TxOut, 2)
var e, ephemkey, pkscr []byte
var nonce, nonce_from uint32
var look4pref bool
sha := sha256.New()
// 6. create a new pub/priv keypair (lets call its pubkey "ephemkey" and privkey "e")
pick_different_e:
e = make([]byte, 32)
rand.Read(e)
defer utils.ClearBuffer(e)
ephemkey = btc.PublicFromPrivate(e, true)
if *verbose {
fmt.Println("e", hex.EncodeToString(e))
fmt.Println("ephemkey", hex.EncodeToString(ephemkey))
}
// 7. IF there is a prefix in the stealth address, brute force a nonce such
// that SHA256(nonce.concate(ephemkey)) first 4 bytes are equal to the prefix.
// IF NOT, then just run through the loop once and pickup a random nonce.
// (probably make the while condition include "or prefix = null" or something to that nature.
look4pref = len(sa.Prefix) > 0 && sa.Prefix[0] > 0
if look4pref {
fmt.Print("Prefix is ", sa.Prefix[0], ":", hex.EncodeToString(sa.Prefix[1:]), " - looking for nonce...")
}
binary.Read(rand.Reader, binary.LittleEndian, &nonce_from)
nonce = nonce_from
for {
binary.Write(sha, binary.LittleEndian, nonce)
sha.Write(ephemkey)
if sa.CheckPrefix(sha.Sum(nil)[:4]) {
break
}
sha.Reset()
nonce++
if nonce == nonce_from {
fmt.Println("EOF")
goto pick_different_e
}
if (nonce & 0xfffff) == 0 {
fmt.Print(".")
}
}
if look4pref {
fmt.Println(uint32(nonce - nonce_from))
}
// 8. Once you have the nonce and the ephemkey, you can create the first output, which is
pkscr = make([]byte, 40)
pkscr[0] = 0x6a // OP_RETURN
pkscr[1] = 38 // length
pkscr[2] = 0x06 // always 6
binary.LittleEndian.PutUint32(pkscr[3:7], nonce)
copy(pkscr[7:40], ephemkey)
res[0] = &btc.TxOut{Pk_script: pkscr}
// 9. Now use ECC multiplication to calculate e*Q where Q = scan_pubkey
// an e = privkey to ephemkey and then hash it.
c := btc.StealthDH(sa.ScanKey[:], e)
if *verbose {
fmt.Println("c", hex.EncodeToString(c))
}
// 10. That hash is now "c". use ECC multiplication and addition to
// calculate D + (c*G) where D = spend_pubkey, and G is the reference
// point for secp256k1. This will give you a new pubkey. (we'll call it D')
Dpr := btc.DeriveNextPublic(sa.SpendKeys[0][:], c)
if *verbose {
fmt.Println("Dpr", hex.EncodeToString(Dpr))
}
// 11. Create a normal P2KH output spending to D' as public key.
adr := btc.NewAddrFromPubkey(Dpr, btc.AddrVerPubkey(*testnet))
res[1] = &btc.TxOut{Value: value, Pk_script: adr.OutScript()}
fmt.Println("Sending to stealth", adr.String())
return
}