RSA Security 5.2.2 manual Six-Step Sequence

The Six-Step Sequence

The Six-Step Sequence

The Crypto-C model generally follows a six-step sequence:

1.Create

2.Set

3.Init

4.Update

5.Final

6.Destroy

In addition, for every application, you must include the necessary header files; we will call this Step 0.

The six-step sequence makes it easier to maintain your code. For example, if you have implemented a message digest routine using MD2 and wish to use SHA1 instead, you simply need to make changes in Steps 2 and 3, Set and Init. The rest of your code can be reused. Similarly, if you originally programmed a routine under the assumption that it would get all the data from a single buffer, and you want to modify it to take data from multiple buffers, you can simply change Step 4, Update.

Note: In some cases, an algorithm may not require an Update step.

The sections in this chapter show the following:

•A six-step encryption example

•A six-step decryption example

•An example using multiple Updates

•A summary of the six-step process

8 R S A B S A F E C r y p t o - C D e v e l o p e r ’s G u i d e