A simple C program to encode and decode Base64 strings without using any third-party libraries:

To convert a HEX-encoded UCS2 string to text with support for the Ukrainian language, you'll need to decode the HEX representation, convert it to UTF-16, and then further convert it to UTF-8 encoding. The following C code demonstrates how to accomplish this: 

To check an RSA1024-SHA1 signature of a string using a certificate (.crt file), you need to follow these steps: