// Encrypts a plaintext message with a temporary key and IV.
func (m *Message) Encrypt() error {
// Generate a new temporary key and the associated block cipher
key := make([]byte, config.PacketCipherBits/8)
if n, err := io.ReadFull(rand.Reader, key); n != len(key) || err != nil {
return err
}
block, err := config.PacketCipher(key)
if err != nil {
return err
}
// Generate a new random counter mode IV and the associated stream cipher
iv := make([]byte, block.BlockSize())
if n, err := io.ReadFull(rand.Reader, iv); n != len(iv) || err != nil {
return err
}
stream := cipher.NewCTR(block, iv)
// Encrypt the message, save the nonces and return
stream.XORKeyStream(m.Data, m.Data)
m.Head.Key = key
m.Head.Iv = iv
m.secure = true
return nil
}
// Decrypts a ciphertext message using the given key and IV.
func (m *Message) Decrypt() error {
// Create the stream cipher for decryption
block, err := config.PacketCipher(m.Head.Key)
if err != nil {
return err
}
stream := cipher.NewCTR(block, m.Head.Iv)
// Decrypt the message, clear out the crypto headers and return
stream.XORKeyStream(m.Data, m.Data)
m.Head.Key = nil
m.Head.Iv = nil
return nil
}
