Question

I am trying to do something in C with the MD5 (and latter trying to do something with the SHA1 algorithm). My main problem is that I never really did anything complex in C, just simple stuff (nothing like pointers to pointers or structs).

I got the md5 algorithm here.

I included the files md5.c and md5.h in my C project (using codeblocks) but the only problem is that I don’t really understand how to use it. I have read and re-read the code and I don’t understand how I use those functions to turn ‘example’ into a MD5 hash.

I haven’t done C programming in a while (mostly php) so I am a bit lost here.
Basically what I am asking is for some examples of usage. They are provided via the md5main.c file but I don’t understand them.

Am I aiming high here? Should I stop all this and start reading the C book again or can anyone give me some pointers and see if I can figure this out.

Thanks.

Answer 1

While I agree with Bill, you should go back to the C book if you want to really understand what you’re doing. But, in an effort to help, I’ve modified and commented some of the code from md5main.c…

const char* testData = "12345";  // this is the data you want to hash
md5_state_t state;  // this is a state object used by the MD5 lib to do "stuff"
                    // just treat it as a black box
md5_byte_t digest[16];  // this is where the MD5 hash will go

// initialize the state structure
md5_init(&state);

// add data to the hasher
md5_append(&state, (const md5_byte_t *)testData, strlen(testData));

// now compute the hash
md5_finish(&state, digest);

// digest will now contain a MD5 hash of the testData input

Hope this helps!