|0.9.0||Aug 29, 2021|
|0.8.1||Jul 20, 2021|
|0.7.1||Oct 25, 2020|
|0.5.1||Jun 11, 2020|
|0.0.0||Oct 6, 2016|
#47 in Cryptography
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Used in 247 crates (44 directly)
Pure Rust implementation of ChaCha20Poly1305 (RFC 8439): an Authenticated Encryption with Associated Data (AEAD) cipher amenable to fast, constant-time implementations in software, based on the ChaCha20 stream cipher and Poly1305 universal hash function.
This crate also contains an implementation of XChaCha20Poly1305: a variant of ChaCha20Poly1305 with an extended 192-bit (24-byte) nonce.
ChaCha20Poly1305 is notable for being simple and fast when implemented in pure software. The underlying ChaCha20 stream cipher uses a simple combination of add, rotate, and XOR instructions (a.k.a. "ARX"), and the Poly1305 hash function is likewise extremely simple.
While it hasn't received approval from certain standards bodies (i.e. NIST) the algorithm is widely used and deployed. Notably it's mandatory to implement in the Transport Layer Security (TLS) protocol. The underlying ChaCha20 cipher is also widely used as a cryptographically secure random number generator, including internal use by the Rust standard library.
All implementations contained in the crate are designed to execute in constant time, either by relying on hardware intrinsics (i.e. AVX2 on x86/x86_64), or using a portable implementation which is only constant time on processors which implement constant-time multiplication.
It is not suitable for use on processors with a variable-time multiplication operation (e.g. short circuit on multiply-by-zero / multiply-by-one, such as certain 32-bit PowerPC CPUs and some non-ARM microcontrollers).
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