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[v3,07/10] crypto: ecc - Use ecc_get_curve_nbits to get number of bits for NIST P521

Message ID 20240223204149.4055630-8-stefanb@linux.ibm.com
State New
Headers show
Series Add support for NIST P521 to ecdsa | expand

Commit Message

Stefan Berger Feb. 23, 2024, 8:41 p.m. UTC 
In ecc_point_mult query for the number of bits when using NIST P521 and
add '2'. The change is required specifically for NIST P521 to pass
mathematical tests on the public key.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 crypto/ecc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
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Patch

diff --git a/crypto/ecc.c b/crypto/ecc.c
index ea7b28b5e00e..89ad45cf2404 100644
--- a/crypto/ecc.c
+++ b/crypto/ecc.c
@@ -1326,7 +1326,10 @@  static void ecc_point_mult(struct ecc_point *result,
 	carry = vli_add(sk[0], scalar, curve->n, ndigits);
 	vli_add(sk[1], sk[0], curve->n, ndigits);
 	scalar = sk[!carry];
-	num_bits = sizeof(u64) * ndigits * 8 + 1;
+	if (ndigits == 9 && !strcmp(curve->name, "nist_521"))
+		num_bits = ecc_curve_get_nbits(curve) + 2;
+	else
+		num_bits = sizeof(u64) * ndigits * 8 + 1;
 
 	vli_set(rx[1], point->x, ndigits);
 	vli_set(ry[1], point->y, ndigits);