A C implementation of the DES cipher with an example of a modern C++ CLI interface.

NOTE: This is a simplified implementation of DES for educational purposes. The DES standard is deprecated and should not be used in production. The library shows example of building C/C++ projects and composition of symmetric exncryption primitives (permutation, substitution, s-boxes, key schedule, etc.)

include/          - C headers (public API)
src/              - C implementation (zero-dependency)
cpp/              - C++ CLI wrapper (modern interface)
tests/            - C test suite
main.cpp          - C++ CLI entry point

make build        # Build C++ CLI (default)
make test         # Run C test suite
make rebuild      # Clean and rebuild
make build-test   # Clean, build and test
make clean        # Remove build artifacts

The core DES implementation is in pure C (src/*.c) with no external dependencies:

# Build and run tests
make test

Test results show encrypt/decrypt roundtrip verification for multiple test vectors.

Modern wrapper with less boilerplate code for command-line interface:

# Show help
./bin/des_cli -h

# Encrypt string (8-byte key required)
./bin/des_cli -k mykey123 -e "Hello World"

# Encrypt with hex output
./bin/des_cli -k mykey123 -e -x "Hello World"

# Decrypt hex
./bin/des_cli -k mykey123 -d -x 63A93A00B066

# Encrypt to file
./bin/des_cli -k mykey123 -e -o encrypted.bin < plain.txt

# Pipe usage
echo "message" | ./bin/des_cli -k mykey123 -e

• Pure C Implementation: Zero external dependencies, portable
• Modern C++ CLI: Clean interface with hex I/O support
• Self-Contained: No external libraries required
• Tested: Self-consistency tests verify encrypt/decrypt roundtrip