Hash (ing) with OpenSSL

We can compute hash with OpenSSL Library. Hash method supported by OpenSSL are SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, MD5, MD4 and others.

Below is Simple example for utilize this library:

1. Declare Used Variable:
   EVP_MD_CTX mdctx;
   const EVP_MD *md;


2. Initialize Variable:
   md = EVP_get_digestbyname("sha1");
   EVP_MD_CTX_init(&mdctx);


3. Initialize Hash Process:
   EVP_DigestInit_ex(&mdctx, md, NULL);


4. Adding data to be hashed:
   EVP_DigestUpdate(&mdctx, (void*)"data-1", strlen("data-1"));


5. Step above can be repeated so all data has been added


6. Finish Hash and get the Hash Result:
   unsigned char *HashResult;
   int HashLen = EVP_MD_size(md);
   HashResult = new unsigned char[HashLen];
   EVP_DigestFinal_ex(&mdctx, HashResult , &HashLen);

Hash Result saved in HashResult Variable.