From 7e337d802aea1f26778d82cd6a542f84d8a51e85 Mon Sep 17 00:00:00 2001
From: Michele Balistreri <michele@bitgamma.com>
Date: Wed, 3 Aug 2022 11:51:23 +0200
Subject: [PATCH] ecdh secret must be 32 bytes

---
 crypto/crypto.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crypto/crypto.go b/crypto/crypto.go
index 5d03567..7352a18 100644
--- a/crypto/crypto.go
+++ b/crypto/crypto.go
@@ -21,7 +21,7 @@ var ErrInvalidCardCryptogram = errors.New("invalid card cryptogram")
 
 func GenerateECDHSharedSecret(priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey) []byte {
 	x, _ := crypto.S256().ScalarMult(pub.X, pub.Y, priv.D.Bytes())
-	return x.Bytes()
+	return x.FillBytes(make([]byte, 32))
 }
 
 func VerifyCryptogram(challenge []byte, pairingPass string, cardCryptogram []byte) ([]byte, error) {