aes-ada

The Advanced Encryption Standard implemented in Ada.

This implementation may not be cryptographically secure.

The AES package provides functions for single blocks and CBC mode with 128, 192 and 256 bit keys.

type Byte is mod 2**8;
type Bytes is array (Natural range <>) of Byte;
subtype Block_Bytes is Bytes(0..15);
subtype Input_Buffer is Bytes;
subtype Init_Vector is Bytes(0..15);
subtype Output_Buffer is Bytes;
subtype Key is Bytes;
subtype AES_128_Key is Key(0..15);
subtype AES_192_Key is Key(0..23);
subtype AES_256_Key is Key(0..31);
type Operation is (Encrypt, Decrypt);

function AES_Block_128(Input: Block_Bytes; K: AES_128_Key; Op: Operation) return Block_Bytes;
function AES_Block_192(Input: Block_Bytes; K: AES_192_Key; Op: Operation) return Block_Bytes;
function AES_Block_256(Input: Block_Bytes; K: AES_256_Key; Op: Operation) return Block_Bytes;

function AES_CBC_128(Input: Input_Buffer; K: AES_128_Key; IV: Init_Vector; Op: Operation) return Output_Buffer;
function AES_CBC_192(Input: Input_Buffer; K: AES_192_Key; IV: Init_Vector; Op: Operation) return Output_Buffer;
function AES_CBC_256(Input: Input_Buffer; K: AES_256_Key; IV: Init_Vector; Op: Operation) return Output_Buffer;

The AES.Util package provides methods for converting between hexadecimal strings and byte arrays.

function Hex_To_Bytes(Hex: String) return Bytes;
function Byte_To_Hex(B: Byte) return String;
function Bytes_To_Hex(Bs: Bytes) return String;

Usage

Encrypt a single block with a 128-bit key

with AES; use AES;
with AES.Util; use AES.Util;
with Ada.Text_IO; use Ada.Text_IO;

procedure Example is
    Input: Block_Bytes := Hex_To_Bytes("00112233445566778899aabbccddeeff");
    Key: AES_128_Key := Hex_To_Bytes("000102030405060708090a0b0c0d0e0f");
    Result: Block_Bytes := AES_Block_128(Input, Key, Encrypt);
begin
    Put_Line(Bytes_To_Hex(Result)); -- 69c4e0d86a7b0430d8cdb78070b4c55a
end Example;

Encrypt several blocks in CBC mode with a 192-bit key

with AES; use AES;
with AES.Util; use AES.Util;
with Ada.Text_IO; use Ada.Text_IO;

procedure Example is
    Input: Input_Buffer := Hex_To_Bytes("f869e8239606a44343f8627cc29a683bd0f431ab80f7121a1a74cb9056d614c5");
    Key: AES_192_Key := Hex_To_Bytes("8e73b0f7da0e6452c810f32b809079e562f8ead2522c6b7b");
    IV: Init_Vector := Hex_To_Bytes("00112233445566778899AABBCCDDEEFF");
    Result: Output_Buffer := AES_CBC_192(Input, Key, IV, Encrypt);
begin
    -- 7162fa4e6f8b0aacaa28051a3c6983540e6070509aa148d8c733f824649f5183c12fd81c5f3652df2be23f3985c85f53
    Put_Line(Bytes_To_Hex(Result));
end Example;

Decrypt a single block with a 256-bit key

with AES; use AES;
with AES.Util; use AES.Util;
with Ada.Text_IO; use Ada.Text_IO;

procedure Example is
    Input: Block_Bytes := Hex_To_Bytes("8ea2b7ca516745bfeafc49904b496089");
    Key: AES_256_Key := Hex_To_Bytes("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f");
    Result: Block_Bytes := AES_Block_256(Input, Key, Decrypt);
begin
    Put_Line(Bytes_To_Hex(Result)); -- 00112233445566778899aabbccddeeff
end Example;

Build and test

Clone the repository and run either gnatmake -D build main.adb or gprbuild. To run the tests, run ./build/main for Linux/Mac or .\build\main.exe for Windows.