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crypto.go
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crypto.go
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package crypto
import (
"crypto/aes"
"crypto/cipher"
"crypto/ecdsa"
"crypto/rand"
"encoding/hex"
"errors"
"fmt"
"github.com/ethereum/go-ethereum/crypto"
)
const (
aesNonceLength = 12
)
// Sign signs the hash of an arbitrary string
func Sign(content string, identity *ecdsa.PrivateKey) (string, error) {
signature, err := crypto.Sign(crypto.Keccak256([]byte(content)), identity)
if err != nil {
return "", err
}
return hex.EncodeToString(signature), nil
}
// VerifySignatures verifys tuples of signatures content/hash/public key
func VerifySignatures(signaturePairs [][3]string) error {
for _, signaturePair := range signaturePairs {
content := crypto.Keccak256([]byte(signaturePair[0]))
signature, err := hex.DecodeString(signaturePair[1])
if err != nil {
return err
}
publicKeyBytes, err := hex.DecodeString(signaturePair[2])
if err != nil {
return err
}
publicKey, err := crypto.UnmarshalPubkey(publicKeyBytes)
if err != nil {
return err
}
recoveredKey, err := crypto.SigToPub(
content,
signature,
)
if err != nil {
return err
}
if crypto.PubkeyToAddress(*recoveredKey) != crypto.PubkeyToAddress(*publicKey) {
return errors.New("identity key and signature mismatch")
}
}
return nil
}
// ExtractSignatures extract from tuples of signatures content a public key
func ExtractSignatures(signaturePairs [][2]string) ([]string, error) {
response := make([]string, len(signaturePairs))
for i, signaturePair := range signaturePairs {
content := crypto.Keccak256([]byte(signaturePair[0]))
signature, err := hex.DecodeString(signaturePair[1])
if err != nil {
return nil, err
}
recoveredKey, err := crypto.SigToPub(
content,
signature,
)
if err != nil {
return nil, err
}
response[i] = fmt.Sprintf("%x", crypto.FromECDSAPub(recoveredKey))
}
return response, nil
}
func EncryptSymmetric(key, plaintext []byte) ([]byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
// Never use more than 2^32 random nonces with a given key because of the risk of a repeat.
salt, err := generateSecureRandomData(aesNonceLength)
if err != nil {
return nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
encrypted, err := aesgcm.Seal(nil, salt, plaintext, nil), nil
if err != nil {
return nil, err
}
return append(encrypted, salt...), nil
}
func DecryptSymmetric(key []byte, cyphertext []byte) ([]byte, error) {
// symmetric messages are expected to contain the 12-byte nonce at the end of the payload
if len(cyphertext) < aesNonceLength {
return nil, errors.New("missing salt or invalid payload in symmetric message")
}
salt := cyphertext[len(cyphertext)-aesNonceLength:]
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
decrypted, err := aesgcm.Open(nil, salt, cyphertext[:len(cyphertext)-aesNonceLength], nil)
if err != nil {
return nil, err
}
return decrypted, nil
}
func containsOnlyZeros(data []byte) bool {
for _, b := range data {
if b != 0 {
return false
}
}
return true
}
func validateDataIntegrity(k []byte, expectedSize int) bool {
if len(k) != expectedSize {
return false
}
if containsOnlyZeros(k) {
return false
}
return true
}
func generateSecureRandomData(length int) ([]byte, error) {
res := make([]byte, length)
_, err := rand.Read(res)
if err != nil {
return nil, err
}
if !validateDataIntegrity(res, length) {
return nil, errors.New("crypto/rand failed to generate secure random data")
}
return res, nil
}