bsaes

README

bsaes - BitSliced AES

Yawning Angel (yawning at schwanenlied dot me)

The AES operations in this package are not implemented using constant-time algorithms. An exception is when running on systems with enabled hardware support for AES that makes these operations constant-time.

-- https://golang.org/pkg/crypto/aes/

bsaes is a portable pure-Go constant time AES implementation based on the excellent code from BearSSL. On appropriate systems, with a sufficiently recent Go runtime, it will transparently call crypto/aes when NewCipher is invoked.

Features:

• Constant time.

• 32 bit and 64 bit variants, with the appropriate one selected at runtime.

• Provides crypto/cipher.Block.

• crypto/cipher.ctrAble support for less-slow CTR-AES mode.

• crypto/cipher.cbcDecAble support for less-slow CBC-AES decryption.

• crypto/cipher.gcmAble support for less-slow GCM-AES. This includes a constant time GHASH.

• The raw guts of the implementations provided as sub-packages, for people to use to implement other things.

Benchmarks:

Primitive	Version	ns/op	MB/s
ECB-AES128	ct32	914	17.50
ECB-AES256	ct32	1268	12.62
CTR-AES128 (16 KiB)	ct32	472010	34.17
CBC-AES128 Decrypt (16 KiB)	ct32	583238	28.09
GCM-AES128 (16 KiB)	ct32	605676	27.05
ECB-AES128	ct64	932	17.16
ECB-AES256	ct64	1258	12.72
CTR-AES128 (16 KiB)	ct64	296016	55.35
CBC-AES128 Decrypt (16 KiB)	ct64	350047	46.81
GCM-AES128 (16 KiB)	ct64	435660	37.61

All numbers taken on an Intel i7-5600U with Turbo Boost disabled, running on linux/amd64.

Documentation

Overview

Package bsaes is a pure-Go bitsliced constant time AES implementation.

Index

• Constants
• func NewCipher(key []byte) (cipher.Block, error)
• func UsingRuntime() bool

Constants

const BlockSize = aes.BlockSize

BlockSize is the AES block size in bytes.

Functions

func NewCipher

func NewCipher(key []byte) (cipher.Block, error)

NewCipher creates and returns a new cipher.Block. The key argument should be the AES key, either 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256.

func UsingRuntime

func UsingRuntime() bool

UsingRuntime returns true iff this package is falling through to the runtime's implementation due to hardware support for constant time operation on the current system.