# extendhash
[](https://crates.io/crates/extendhash)
[](https://docs.rs/extendhash)
**extendhash** is a Rust library to compute hash extensions. Currently
only MD5 is supported, but more hash algorithms are planned in the future.
## Usage
```rust
use extendhash::md5;
let secret_data = "This is a secret!".as_bytes();
let hash = md5::compute_hash(secret_data);
let secret_data_length = secret_data.len();
// Now we try computing a hash extension,
// assuming that `secret_data` is not available.
// We only need `hash` and `secret_data_length`.
let appended_message = "Appended message.".as_bytes();
let combined_hash = md5::extend_hash(
hash, secret_data_length, appended_message);
// Now we verify that `combined_hash` matches the
// concatenation (note the intermediate padding):
let mut combined_data = Vec::<u8>::new();
combined_data.extend_from_slice(secret_data);
let intermediate_padding = md5::padding_for_length(secret_data_length);
combined_data.extend_from_slice(intermediate_padding.as_slice());
combined_data.extend_from_slice(appended_message);
assert_eq!(combined_hash, md5::compute_hash(combined_data.as_slice()));
```
## License
Licensed under either of
* Apache License, Version 2.0
([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license
([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
## Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.