𓍯𓂃 RSASSAPSS

Introduction

The RSASSAPSS library provides functionality to verify RSASSA-PSS signatures with MGF1 mask generation function.

Users may provide custom hash functions via Parameters struct. However, the usage of sha256 is recommended. The RSASSA-PSS signature verification costs ~340k gas.

Learn more about the algorithm here.

Functions

To use the RSASSAPSS library, you need to import it.

import "@solarity/solidity-lib/libs/crypto/RSASSAPSS.sol";

And optionally bind it to the type with the using statement.

using RSASSAPSS for *;

verifySha256

function verifySha256(
    bytes memory message_,
    bytes memory s_,
    bytes memory e_,
    bytes memory n_
) internal view returns (bool);

Description

Same as verify but with sha256 hash function preconfiguration.

verify

function verify(
    RSASSAPSS.Parameters memory params_,
    bytes memory message_,
    bytes memory s_,
    bytes memory e_,
    bytes memory n_
) internal view returns (bool);

Description

Verifies RSAPSS-SSA signature with custom parameters.

Parameters:

Name	Type	Description
params	struct RSASSAPSS.Parameters	The parameters to specify the hash length, salt length, and hash function of choice
message	bytes	The arbitrary message to be verified
s	bytes	The "encrypted" signature
e	bytes	The public key exponent. 65537 is a recommended value
n	bytes	The modulus of a public key

Where RSASSAPSS.Parameters consist of:

Name	Type	Description
hashLength	uint256	The hash function output length in bytes
saltLength	uint256	The pss encoding salt length in bytes
hasher	function (bytes) pure returns (bytes)	The function-pointer to a custom hash function

Example

function verifySha256(
    bytes calldata message_,
    bytes calldata s_,
    bytes calldata e_,
    bytes calldata n_
) external view returns (bool) {
    return message_.verifySha256(s_, e_, n_);
}