Crate base64ct[−][src]

Expand description

Pure Rust implementation of Base64 encoding (RFC 4648, section 4) with a constant-time no_std-friendly implementation.

About

This crate implements several Base64 variants in constant-time.

The padded variants require (=) padding. Unpadded variants expressly reject such padding.

Whitespace is expressly disallowed.

Minimum Supported Rust Version

This crate requires Rust 1.47 at a minimum.

We may change the MSRV in the future, but it will be accompanied by a minor version bump.

Usage

Allocating (enable `alloc` crate feature)

use base64ct::{Base64, Encoding};

let bytes = b"example bytestring!";
let encoded = Base64::encode_string(bytes);
assert_eq!(encoded, "ZXhhbXBsZSBieXRlc3RyaW5nIQ==");

let decoded = Base64::decode_vec(&encoded).unwrap();
assert_eq!(decoded, bytes);

Heapless `no_std` usage

use base64ct::{Base64, Encoding};

const BUF_SIZE: usize = 128;

let bytes = b"example bytestring!";
assert!(Base64::encoded_len(bytes) <= BUF_SIZE);

let mut enc_buf = [0u8; BUF_SIZE];
let encoded = Base64::encode(bytes, &mut enc_buf).unwrap();
assert_eq!(encoded, "ZXhhbXBsZSBieXRlc3RyaW5nIQ==");

let mut dec_buf = [0u8; BUF_SIZE];
let decoded = Base64::decode(encoded, &mut dec_buf).unwrap();
assert_eq!(decoded, bytes);

Implementation

Implemented using bitwise arithmetic alone without any lookup tables or data-dependent branches, thereby providing portable “best effort” constant-time operation.

Not constant-time with respect to message length (only data).

Adapted from the following constant-time C++ implementation of Base64:

https://github.com/Sc00bz/ConstTimeEncoding/blob/master/base64.cpp