# [RustCrypto]: GF(2^128) "dbl" operation
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[![Docs][docs-image]][docs-link]
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![Apache2/MIT licensed][license-image]
![Rust Version][rustc-image]
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Double operation in Galois Field GF(2^128) as used by e.g. CMAC/PMAC.
Also known as "multiply-by-x", the operation is performed in the finite field
represented using the primitive polynomial x^128 + x^7 + x^2 + x + 1.
## License
Licensed under either of:
* [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0)
* [MIT license](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.
[//]: # (badges)
[crate-image]: https://img.shields.io/crates/v/dbl.svg
[crate-link]: https://crates.io/crates/dbl
[docs-image]: https://docs.rs/dbl/badge.svg
[docs-link]: https://docs.rs/dbl/
[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
[rustc-image]: https://img.shields.io/badge/rustc-1.65+-blue.svg
[chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
[chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260052-utils
[build-image]: https://github.com/RustCrypto/utils/workflows/dbl/badge.svg?branch=master&event=push
[build-link]: https://github.com/RustCrypto/utils/actions/workflows/dbl.yml
[//]: # (general links)
[RustCrypto]: https://github.com/rustcrypto