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Remove derive_subkey() as it is not needed when deriving a key from passphrase

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Juhani Krekelä 2021-04-08 20:43:56 +03:00
parent d4ed30a592
commit 08c8d33b20
1 changed files with 0 additions and 20 deletions
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puer.c
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@ -64,26 +64,6 @@ void word2bytes(unsigned char *bytes, uint32_t word) {
bytes[3] = word>>24;
}
void derive_subkey(uint32_t key[4], uint32_t nonce[6], uint32_t subkey[4]) {
// We are using an extended nonce construction with 192 bit nonces.
// The first 128 bits of nonce are encrypted using xxtea128 with
// the provided key, in order to derive a subkey that is then used
// alongside the remaining nonce to do the actual encryption.
//
// This is, as far as I can tell, not a standard construction. I
// have based it on xchacha20, with the understanding that it
// should not matter if the function used to derive the subkey is
// reversible or not, since an attacker doesn't know the original
// key and the original key is used only in this derivation.
subkey[0] = nonce[0];
subkey[1] = nonce[1];
subkey[2] = nonce[2];
subkey[3] = nonce[3];
xxtea128(key, subkey);
}
struct hashstate {
// A_n and B_n of the MDC-2 algorithm
uint32_t a[4];