README.md

soterec

Package soterec implements elliptic curve cryptography needed for working with Soter (secp256k1 only for now). It is designed so that it may be used with the standard crypto/ecdsa packages provided with go. A comprehensive suite of test is provided to ensure proper functionality. Package soterec was originally based on work from ThePiachu which is licensed under the same terms as Go, but it has signficantly diverged since then. The btcsuite developers original is licensed under the liberal ISC license.

Although this package was primarily written for soterd, it has intentionally been designed so it can be used as a standalone package for any projects needing to use secp256k1 elliptic curve cryptography.

Installation and Updating

$ go get -u github.com/soteria-dag/soterd/soterec

Examples

Sign Message

Demonstrates signing a message with a secp256k1 private key that is first parsed form raw bytes and serializing the generated signature.

// Decode a hex-encoded private key.
pkBytes, err := hex.DecodeString("22a47fa09a223f2aa079edf85a7c2d4f87" +
    "20ee63e502ee2869afab7de234b80c")
if err != nil {
    fmt.Println(err)
    return
}
privKey, pubKey := soterec.PrivKeyFromBytes(soterec.S256(), pkBytes)

// Sign a message using the private key.
message := "test message"
messageHash := chainhash.DoubleHashB([]byte(message))
signature, err := privKey.Sign(messageHash)
if err != nil {
    fmt.Println(err)
    return
}

// Serialize and display the signature.
fmt.Printf("Serialized Signature: %x\n", signature.Serialize())

// Verify the signature for the message using the public key.
verified := signature.Verify(messageHash, pubKey)
fmt.Printf("Signature Verified? %v\n", verified)

Output

Serialized Signature: 304402201008e236fa8cd0f25df4482dddbb622e8a8b26ef0ba731719458de3ccd93805b022032f8ebe514ba5f672466eba334639282616bb3c2f0ab09998037513d1f9e3d6d
Signature Verified? true

Verify Signature

Demonstrates verifying a secp256k1 signature against a public key that is first parsed from raw bytes. The signature is also parsed from raw bytes.

// Decode hex-encoded serialized public key.
pubKeyBytes, err := hex.DecodeString("02a673638cb9587cb68ea08dbef685c" +
    "6f2d2a751a8b3c6f2a7e9a4999e6e4bfaf5")
if err != nil {
    fmt.Println(err)
    return
}
pubKey, err := soterec.ParsePubKey(pubKeyBytes, soterec.S256())
if err != nil {
    fmt.Println(err)
    return
}

// Decode hex-encoded serialized signature.
sigBytes, err := hex.DecodeString("30450220090ebfb3690a0ff115bb1b38b" +
    "8b323a667b7653454f1bccb06d4bbdca42c2079022100ec95778b51e707" +
    "1cb1205f8bde9af6592fc978b0452dafe599481c46d6b2e479")

if err != nil {
    fmt.Println(err)
    return
}
signature, err := soterec.ParseSignature(sigBytes, soterec.S256())
if err != nil {
    fmt.Println(err)
    return
}

// Verify the signature for the message using the public key.
message := "test message"
messageHash := chainhash.DoubleHashB([]byte(message))
verified := signature.Verify(messageHash, pubKey)
fmt.Println("Signature Verified?", verified)

Output

Signature Verified? true

Encryption

Demonstrates encrypting a message for a public key that is first parsed from raw bytes, then decrypting it using the corresponding private key.

// Decode the hex-encoded pubkey of the recipient.
pubKeyBytes, err := hex.DecodeString("04115c42e757b2efb7671c578530ec191a1" +
    "359381e6a71127a9d37c486fd30dae57e76dc58f693bd7e7010358ce6b165e483a29" +
    "21010db67ac11b1b51b651953d2") // uncompressed pubkey
if err != nil {
    fmt.Println(err)
    return
}
pubKey, err := soterec.ParsePubKey(pubKeyBytes, soterec.S256())
if err != nil {
    fmt.Println(err)
    return
}

// Encrypt a message decryptable by the private key corresponding to pubKey
message := "test message"
ciphertext, err := soterec.Encrypt(pubKey, []byte(message))
if err != nil {
    fmt.Println(err)
    return
}

// Decode the hex-encoded private key.
pkBytes, err := hex.DecodeString("a11b0a4e1a132305652ee7a8eb7848f6ad" +
    "5ea381e3ce20a2c086a2e388230811")
if err != nil {
    fmt.Println(err)
    return
}
// note that we already have corresponding pubKey
privKey, _ := soterec.PrivKeyFromBytes(soterec.S256(), pkBytes)

// Try decrypting and verify if it's the same message.
plaintext, err := soterec.Decrypt(privKey, ciphertext)
if err != nil {
    fmt.Println(err)
    return
}

fmt.Println(string(plaintext))

Output

test message

Decryption

Demonstrates decrypting a message using a private key that is first parsed from raw bytes.

// Decode the hex-encoded private key.
pkBytes, err := hex.DecodeString("a11b0a4e1a132305652ee7a8eb7848f6ad" +
    "5ea381e3ce20a2c086a2e388230811")
if err != nil {
    fmt.Println(err)
    return
}

privKey, _ := soterec.PrivKeyFromBytes(soterec.S256(), pkBytes)

ciphertext, err := hex.DecodeString("35f644fbfb208bc71e57684c3c8b437402ca" +
    "002047a2f1b38aa1a8f1d5121778378414f708fe13ebf7b4a7bb74407288c1958969" +
    "00207cf4ac6057406e40f79961c973309a892732ae7a74ee96cd89823913b8b8d650" +
    "a44166dc61ea1c419d47077b748a9c06b8d57af72deb2819d98a9d503efc59fc8307" +
    "d14174f8b83354fac3ff56075162")

// Try decrypting the message.
plaintext, err := soterec.Decrypt(privKey, ciphertext)
if err != nil {
    fmt.Println(err)
    return
}

fmt.Println(string(plaintext))

Output

test message

License

Package soterec is licensed under the copyfree ISC License except for soterec.go and soterec_test.go which is under the same license as Go.