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Merged
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Aug 14, 2022
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crypto_kx: select x25519-dalek backend automatically #60

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11 changes: 6 additions & 5 deletions crypto_kx/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -17,14 +17,15 @@ rust-version = "1.56"
blake2 = { version = "0.10", default-features = false }
rand_core = "0.6"

[target.'cfg(target_pointer_width = "32")'.dependencies]
x25519-dalek = { version = "1", default-features = false, features = ["u32_backend"] }

[target.'cfg(target_pointer_width = "64")'.dependencies]
x25519-dalek = { version = "1", default-features = false, features = ["u64_backend"] }

# optional dependencies
serdect = { version = "0.1", optional = true, default-features = false }

[dependencies.x25519-dalek]
version = "1"
default-features = false
features = ["u64_backend"] # to allow --no-default-features

[target.'cfg(target_family = "wasm")'.dependencies]
getrandom = { version = "0.2", default-features = false, features = ["js"] }

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19 changes: 19 additions & 0 deletions crypto_kx/README.md
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Expand Up @@ -11,6 +11,25 @@ Pure Rust implementation of [libsodium]'s [`crypto_kx`] primitive.

[Documentation][docs-link]

## About

Imagine Alice wants to open a safe communication channel with Betty,
using something like [`crypto_secretstream`]. They first need to agree on
a shared secret.

To obtain this shared secret, Diffie-Hellman can be used, which works as follows:
Suppose both Alice and Betty know the public key of each other.
Then they use their private key and the other's public key to generate a
secret. This secret is the same for both Alice and Betty, as described by
the Diffie-Hellman algorithm.
No eavesdropper can know what the secret is, as they only know the public keys, but
not the private keys.

Using the same key for sending and receiving might pose cryptographic
issues and/or reduce the overall throughput.
So when computing the shared secret, you actually get two keys,
one for each direction.

## License

Licensed under either of:
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40 changes: 10 additions & 30 deletions crypto_kx/src/lib.rs
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Original file line number Diff line number Diff line change
@@ -1,27 +1,11 @@
//! Pure Rust implementation of the [`crypto_kx`] key exchange
//! from [NaCl]-family libraries (e.g. libsodium, TweetNaCl)
//! which uses [BLAKE2].
//!
//! # Introduction
//!
//! Imagine Alice wants to open a safe communication channel with Betty,
//! using something like [`crypto_secretstream`]. They first need to agree on
//! a shared secret.
//!
//! To obtain this shared secret, Diffie-Hellman can be used, which works as follows:
//! Suppose both Alice and Betty know the public key of each other.
//! Then they use their private key and the other's public key to generate a
//! secret. This secret is the same for both Alice and Betty, as described by
//! the Diffie-Hellman algorithm.
//! No eavesdropper can know what the secret is, as they only know the public keys, but
//! not the private keys.
//!
//! Using the same key for sending and receiving might pose cryptographic
//! issues and/or reduce the overall throughput.
//! So when computing the shared secret, you actually get two keys,
//! one for each direction.
//!
//! # Usage
#![no_std]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg",
html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg"
)]
#![warn(missing_docs, rust_2018_idioms)]

//! ## Usage
//!
//! ```rust
//! use crypto_kx::*;
Expand All @@ -46,12 +30,8 @@
//! [`crypto_secretstream`]: https://github.com/RustCrypto/nacl-compat/tree/master/crypto_secretstream
//! [BLAKE2]: https://github.com/RustCrypto/hashes/tree/master/blake2

#![no_std]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg",
html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg"
)]
#![warn(missing_docs, rust_2018_idioms)]
#[cfg(not(any(target_pointer_width = "32", target_pointer_width = "64")))]
compile_error!("`crypto-box` requires either a 32-bit or 64-bit target");

mod keypair;
mod keys;
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