winapi-encryption: cngcrypt

A file encryption program that uses the WinAPI library Cryptography API: Next Generation. The compiled binary name is cngcrypt as this is easier to remember and write. This program only works on Windows and can be compiled by using CMake.

WARNING: This is a toy project. It might be cryptographically insecure! Do NOT use in production!

How to use

cngcrypt [FLAGS] <SECRET> <INPUT> <OUTPUT>

• FLAGS must use specify at least one flag
• SECRET password used to derive the AES key from
• INPUT input file
• OUTPUT output file

Flags

• -h prints help information and exits
• -e encrypt input file to output file
• -d decrypt input file to output file
• -S print derived AES key and IV, optional

Technical details

This program uses AES-128 to encrypt the files. The AES key is derived by generating a SHA-256 hash of the password and collapsing the hash into 128-bit using XOR (see data_half_collapse() in crypto.c). The IV is generated randomly using BCryptGenRandom().

Encrypted file

The encrypted file consists of three parts. The first 8 bytes are used to store the original file length. The next 16 bytes are used to store the IV. After that the actual encrypted contents start.