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crypto/secp256k1: add safety comments

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This commit is contained in:
Felix Lange 2017-01-12 15:37:48 +01:00
parent 6a2c12a2dc
commit 97fcd221f2
2 changed files with 5 additions and 0 deletions
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1
crypto/secp256k1/curve.go
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@ -223,6 +223,7 @@ func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int,
if len(scalar) > 32 { if len(scalar) > 32 {
panic("can't handle scalars > 256 bits") panic("can't handle scalars > 256 bits")
} }
// NOTE: potential timing issue
padded := make([]byte, 32) padded := make([]byte, 32)
copy(padded[32-len(scalar):], scalar) copy(padded[32-len(scalar):], scalar)
scalar = padded scalar = padded

4
crypto/secp256k1/secp256.go
View file

@ -72,6 +72,10 @@ var (
// Sign creates a recoverable ECDSA signature. // Sign creates a recoverable ECDSA signature.
// The produced signature is in the 65-byte [R || S || V] format where V is 0 or 1. // The produced signature is in the 65-byte [R || S || V] format where V is 0 or 1.
//
// The caller is responsible for ensuring that msg cannot be chosen
// directly by an attacker. It is usually preferable to use a cryptographic
// hash function on any input before handing it to this function.
func Sign(msg []byte, seckey []byte) ([]byte, error) { func Sign(msg []byte, seckey []byte) ([]byte, error) {
if len(msg) != 32 { if len(msg) != 32 {
return nil, ErrInvalidMsgLen return nil, ErrInvalidMsgLen