Copyright © 2017-2021 Guilherme Andrade
Version: 1.1.1
Authors: Guilherme Andrade (erlffx(at)gandrade(dot)net).
erlffx
: Format Preserving Encryption - FFX for Erlang
erlffx
is an Erlang implementation of the mechanism described in the 2010 paper The FFX Mode of Operation for Format-Preserving Encryption by Bellare, Rogaway and Spies. It is based on an existing Java implementation by Michael Tandy.
* AES-128 / AES-192 (only Erlang 19 and up) / AES-256 keys are supported (CBC mode) * Any positive word length is supported * Any radix / alphabet size between 2 and 255 is acceptable (10 by default) * Optional 'tweak' values may be defined * Number of rounds is configurable (10 by default)
The code was successfully tested on generations 17, 18 and 19 of Erlang/OTP; the unit tests themselves were written using the following lists of test vectors: * AES FFX Test Vector Data * FF1 samples
% AES-128 CBC / 10-digit decimal words
AesKey = <<43,126,21,22,40,174,210,166,171,247,21,136,9,207,79,60>>,
ValueLength = 10,
Config = erlffx:config(AesKey, ValueLength).
Encrypted = erlffx:encrypt(Config, 123456789). % 2433477484
Decrypted = erlffx:decrypt(Config, Encrypted). % 123456789
% AES-128 CBC / 10-digit decimal words / custom tweak
AesKey = <<43,126,21,22,40,174,210,166,171,247,21,136,9,207,79,60>>,
ValueLength = 10,
Config = erlffx:config(AesKey, ValueLength, #{ tweak => "9876543210" }).
Encrypted = erlffx:encrypt(Config, 123456789). % 6124200773
Decrypted = erlffx:decrypt(Config, Encrypted). % 123456789
% AES-128 CBC / 16-digit base-36 words / custom tweak
AesKey = <<43,126,21,22,40,174,210,166,171,247,21,136,9,207,79,60>>,
ValueLength = 16,
Config = erlffx:config(AesKey, ValueLength, #{ tweak => "TQF9J5QDAGSCSPB1", radix => 36 }).
Encrypted = erlffx:encrypt(Config, 36#C4XPWULBM3M863JH). % 36#C8AQ3U846ZWH6QZP
Decrypted = erlffx:decrypt(Config, Encrypted). % 36#C4XPWULBM3M863JH
% AES-256 CBC / 6-digit binary words
AesKey = <<43,126,21,22,40,174,210,166,171,247,21,136,9,207,79,60,
239,67,89,216,213,128,170,79,127,3,109,111,4,252,106,148>>,
ValueLength = 6,
Config = erlffx:config(AesKey, ValueLength, #{ radix => 2 }).
Encrypted = erlffx:encrypt(Config, 2#000001). % 2#100100
Decrypted = erlffx:decrypt(Config, Encrypted). % 2#000001
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