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Copy bit twiddling from libgcrypt/cipher/ecc.c

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Reversed order buisness agrees with KC's experence from gnunet-rs
This commit is contained in:
Jeff Burdges 2016-08-08 10:38:07 +02:00
parent 0fd6cf19af
commit 7958464696
1 changed files with 14 additions and 1 deletions
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15
src/util/crypto.c
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@ -194,7 +194,20 @@ TALER_setup_fresh_coin (const struct TALER_TransferSecretP *secret_seed,
"taler-coin-derivation",
strlen ("taler-coin-derivation"),
NULL, 0));
/* FIXME: twiddle the bits of the private key */
/* Taken from like 170-172 of libgcrypt/cipher/ecc.c
* We note that libgcrypt stores the private key in the reverse order
* from many Ed25519 implementatons. */
fc->coin_priv[0] &= 0x7f; /* Clear bit 255. */
fc->coin_priv[0] |= 0x40; /* Set bit 254. */
fc->coin_priv[31] &= 0xf8; /* Clear bits 2..0 so that d mod 8 == 0 */
/* FIXME: Run GNUNET_CRYPTO_ecdhe_key_create several times and inspect
* the output to verify that the same bits are set and cleared.
* Is it worth also adding a test case that runs gcry_pk_testkey on
* this key after first parsing it into libgcrypt's s-expression mess
* ala decode_private_eddsa_key from gnunet/src/util/crypto_ecc.c?
* It'd run check_secret_key but not test_keys from libgcrypt/cipher/ecc.c */
}