98c9191679
* only support HMAC with 32 byte keys * includes HMAC in the trait to be generic * re-added HAMC test
81 lines
2.9 KiB
Rust
81 lines
2.9 KiB
Rust
// Copyright 2021 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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use super::hmac::hmac_256;
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use super::Hash256;
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const HASH_SIZE: usize = 32;
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/// Computes the HKDF with empty salt and 256 bit (one block) output.
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///
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/// # Arguments
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///
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/// * `ikm` - Input keying material
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/// * `info` - Optional context and application specific information
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///
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/// This implementation is equivalent to the below hkdf, with `salt` set to the
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/// default block of zeros and the output length l as 32.
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pub fn hkdf_empty_salt_256<H>(ikm: &[u8], info: &[u8]) -> [u8; HASH_SIZE]
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where
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H: Hash256,
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{
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// Salt is a zero block here.
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let prk = hmac_256::<H>(&[0; HASH_SIZE], ikm);
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// l is implicitly the block size, so we iterate exactly once.
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let mut t = info.to_vec();
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t.push(1);
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hmac_256::<H>(&prk, t.as_slice())
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}
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#[cfg(test)]
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mod test {
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use super::super::sha256::Sha256;
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use super::*;
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use arrayref::array_ref;
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#[test]
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fn test_hkdf_empty_salt_256_sha256_vectors() {
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// Test vectors generated by pycryptodome using:
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// HKDF(b'0', 32, b'', SHA256, context=b'\x00').hex()
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let test_okms = [
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hex::decode("f9be72116cb97f41828210289caafeabde1f3dfb9723bf43538ab18f3666783a")
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.unwrap(),
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hex::decode("f50f964f5b94d62fd1da9356ab8662b0a0f5b8e36e277178b69b6ffecf50cf44")
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.unwrap(),
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hex::decode("fc8772ceb5592d67442dcb4353cdd28519e82d6e55b4cf664b5685252c2d2998")
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.unwrap(),
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hex::decode("62831b924839a180f53be5461eeea1b89dc21779f50142b5a54df0f0cc86d61a")
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.unwrap(),
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hex::decode("6991f00a12946a4e3b8315cdcf0132c2ca508fd17b769f08d1454d92d33733e0")
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.unwrap(),
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hex::decode("0f9bb7dddd1ec61f91d8c4f5369b5870f9d44c4ceabccca1b83f06fec115e4e3")
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.unwrap(),
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hex::decode("235367e2ab6cca2aba1a666825458dba6b272a215a2537c05feebe4b80dab709")
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.unwrap(),
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hex::decode("96e8edad661da48d1a133b38c255d33e05555bc9aa442579dea1cd8d8b8d2aef")
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.unwrap(),
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];
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for (i, okm) in test_okms.iter().enumerate() {
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// String of number i.
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let ikm = i.to_string();
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// Byte i.
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let info = [i as u8];
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assert_eq!(
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&hkdf_empty_salt_256::<Sha256>(&ikm.as_bytes(), &info[..]),
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array_ref!(okm, 0, 32)
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);
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}
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}
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}
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