forked from gtank/cryptopasta
/
encrypt.go
65 lines (52 loc) · 1.58 KB
/
encrypt.go
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// Provides symmetric authenticated encryption using 256-bit AES-GCM with a
// random nonce.
package cryptopasta
import (
"crypto/aes"
"crypto/cipher"
)
const aesKeySize = 32 // force 256-bit AES
// GenerateEncryptionKey generates a random 256-bit key for Encrypt() and
// Decrypt().
func GenerateEncryptionKey() ([]byte, error) {
return generateBytes(aesKeySize)
}
// Encrypt encrypts data using 256-bit AES-GCM. This both hides the content of
// the data and provides a check that it hasn't been altered. Output takes the
// form nonce|ciphertext|tag where '|' indicates concatenation.
func Encrypt(plaintext, key []byte) (ciphertext []byte, err error) {
if len(key) != aesKeySize {
return nil, aes.KeySizeError(len(key))
}
aes, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(aes)
if err != nil {
return nil, err
}
nonce, err := generateBytes(gcm.NonceSize())
if err != nil {
return nil, err
}
return gcm.Seal(nonce, nonce, plaintext, nil), nil
}
// Decrypt decrypts data using 256-bit AES-GCM. This both hides the content of
// the data and provides a check that it hasn't been altered. Expects input
// form nonce|ciphertext|tag where '|' indicates concatenation.
func Decrypt(ciphertext, key []byte) (plaintext []byte, err error) {
if len(key) != aesKeySize {
return nil, aes.KeySizeError(len(key))
}
aes, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(aes)
if err != nil {
return nil, err
}
return gcm.Open(nil, ciphertext[:gcm.NonceSize()],
ciphertext[gcm.NonceSize():], nil)
}