RSA Security 5.2.2 manual Introductory Example, Include Files, Creating an Algorithm Object

Introductory Example

Introductory Example

The CD containing the Crypto-C library distribution also includes sample source code to accompany this Developer’s Guide. One of the files on that CD, introex.c, is an example of converting the Introductory Example into a program. Later in this manual are instructions on writing code for many Crypto-C operations. There are sample programs on the CD to accompany all the topics covered.

With the RSA BSAFE Crypto-C Reference Manual handy, we will encrypt the sentence, “Encrypt this sentence.” To do this, we will use what is called a stream cipher, that is, an encryption method that encrypts data one character at a time, in a single stream.

The cipher we will use is called the RC4 cipher. This cipher can take a key size from 1 to 256 bytes. The RC4 cipher creates a “key stream” based on the key and XORs the stream of data with the key stream to create ciphertext.

The example in this section corresponds to the file introex.c.

Step 0: Include Files

You must include the following header file and the Crypto-C library in every application you write using Crypto-C:

#include “bsafe.h”

When writing a Crypto-C application, include bsafe.h. If you want to use the DEMO_ALGORITHM_CHOOSER, see Selecting an Algorithm Chooser on page

15.In addition, you must compile and link in tstdlib.c, which contains the memory management functions called by the Crypto-C library.

Note: For backward compatibility, the BSAFE 2.x include file names, global.h and bsafe2.h, are still valid. If your source code contains the older names, you should not have any problems.

Step 1: Creating an Algorithm Object

Whatever operation Crypto-C performs, it does so from an algorithm object. An algorithm object is used to hold information about an algorithm’s parameters and to keep a context during a cryptographic operation such as encryption or decryption. For our example, we will build an algorithm object that performs encryption.

You build an algorithm object in Steps 1 to 3. As you go through these steps, you

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