JezK
Edit File: constant_time.c
// Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or // implied. // See the License for the specific language governing permissions and // limitations under the License. uint8_t Cryptography_constant_time_bytes_eq(uint8_t *a, size_t len_a, uint8_t *b, size_t len_b) { size_t i = 0; uint8_t mismatch = 0; if (len_a != len_b) { return 0; } for (i = 0; i < len_a; i++) { mismatch |= a[i] ^ b[i]; } /* Make sure any bits set are copied to the lowest bit */ mismatch |= mismatch >> 4; mismatch |= mismatch >> 2; mismatch |= mismatch >> 1; /* Now check the low bit to see if it's set */ return (mismatch & 1) == 0; }