// prepare key for low-level poly1305.Sum(): r||n
func poly1305PrepareKey(nonce []byte, key *MACKey) [32]byte {
var k [32]byte
maskKey(key)
cipher, err := aes.NewCipher(key.K[:])
if err != nil {
panic(err)
}
cipher.Encrypt(k[16:], nonce[:])
copy(k[:16], key.R[:])
return k
}
// stringhash computes generic string hash. Uses k as the key for AES
// cipher.
func stringhash(s string, k []byte) []byte {
a := bytes_to_a32(paddnull([]byte(s), 4))
h := []uint32{0, 0, 0, 0}
for i, v := range a {
h[i&3] ^= v
}
hb := a32_to_bytes(h)
cipher, _ := aes.NewCipher(k)
for i := 16384; i > 0; i-- {
cipher.Encrypt(hb, hb)
}
ha := bytes_to_a32(paddnull(hb, 4))
return a32_to_base64([]uint32{ha[0], ha[2]})
}
func Encrypt(text, key []byte) ([]byte, error) {
// Create cipher and pad text
cipher, padded, err := cipherAndPaddedText(text, key)
if err != nil {
return nil, err
}
keysize := len(key)
// Encrypt each block
for i := 0; i < len(padded)/keysize; i += keysize {
cipher.Encrypt(padded[i:i+keysize], padded[i:i+keysize])
}
return padded[:len(text)], nil
}