76 lines
2.8 KiB
Markdown
76 lines
2.8 KiB
Markdown
Advanced Encryption Standard (AES) implementation in C
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======================================================
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AES is the most widely adopted symmetric encryption standard nowadays. This repository contains an implementation in C of the AES-128 algorithm. The program takes two arguments: a 32-bytes hexadecimal string representing the 128-bit input block, and another 32-bytes hexadecimal string representing the 128-bit key. It then outputs the corresponding ciphertext in hexadecimal form.
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AES Reference: https://doi.org/10.6028/NIST.FIPS.197-upd1
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Screenshot taken after building the project with the build.bat file.
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Installation
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------------
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First make sure you have installed the GCC compiler v8.1.0 or above.
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The `gcc --version` command should output:
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```
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gcc (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 8.1.0
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Copyright (C) 2018 Free Software Foundation, Inc.
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This is free software; see the source for copying conditions. There is NO
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warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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```
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Then, clone this repository in any location on your computer and double-click on `build.bat`.
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You should now see the following program's output:
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```
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CIPHERTEXT: 732281c0a0aab8f7a54a0c67a0c45ecf
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```
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The corresponding plaintext and key to obtain this ciphertext are encoded within the `build.bat` file.
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Usage and test vectors
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----------------------
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The program takes two arguments: a 32-bytes hexadecimal string representing the 128-bit input block, and another 32-bytes hexadecimal string representing the 128-bit key. It then outputs the corresponding ciphertext in hexadecimal form.
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You can find some test vectors on the official NIST website [on this page](https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/block-ciphers).
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For example, with the following sample data set:
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```
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KEY = 00000000000000000000000000000000
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PLAINTEXT = 6a84867cd77e12ad07ea1be895c53fa3
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```
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The program should output:
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```
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CIPHERTEXT: 732281c0a0aab8f7a54a0c67a0c45ecf
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```
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To check this output, build the project and then execute this command:
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```
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main.exe 6a84867cd77e12ad07ea1be895c53fa3 00000000000000000000000000000000
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```
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You should now see the ciphertext `732281c0a0aab8f7a54a0c67a0c45ecf`.
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Future work
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-----------
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A few ideas to improve this project:
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- Add decryption part.
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- Test the implementation in ECB or CBC block cipher modes.
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- Rewrite the key expansion function in a cleaner way.
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- Add features for file encryption.
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License
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-------
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This work is shared under the [MIT license](LICENSE).
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The AES S-Box initialization function has not been written by me and have been taken from:
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https://en.wikipedia.org/wiki/Rijndael_S-box (Accessed on March 21, 2025)
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Original licence: CC BY-SA 4.0
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