This is a copy of Kocher implementation back in 1997. I added a very simple test file that uses Kocher's code to encrypt and decrypt a text line.

How the implementation works

Please see the Wikipedia page for how the algorithm works internally. For developer, we need to understand a few important features:

• Blowfish is a symmetric-key block cipher. Which means the same key is used for encrypting and decrypting.
• The algorithm works with 8 bytes block-based. Each block is processed independently to each other.
• The caller needs to split that 8 bytes block into 2 parts, Left and Right. In my test, 4 chars will be copied into a unsigned long variable.

Run the code

blowfish_test.c, blowfish.c, blowfish.h were written by Paul Kocher. Run it with:

gcc -Wall blowfish_test.c blowfish.c -o b; ./b
# 272A5DF333FD2 33A2830A71BB4
# Test encryption failed.
# Test decryption OK

To run my simple test:

gcc -Wall test_bf.c blowfish.c -o test_bf; ./test_bf
# length: 24
# plaintext:  This is a random message
# encrypted:  l+����*u�&��2�K�[�C�,\�
# decrypted:  This is a random message