RSA Security 5.2.2 manual Surrender Context, Description of AIX962RandomV0 instead of AISHA1Random

System Considerations In Crypto-C

description of AI_X962Random_V0 instead of AI_SHA1Random:

B_ALGORITHM_METHOD *RSA_SAMPLE_CHOOSER[] = { &AM_SHA_RANDOM,

&AM_RSA_KEY_GEN,

&AM_RSA_ENCRYPT, &AM_RSA_CRT_DECRYPT, (B_ALGORITHM_METHOD *)NULL_PTR

};

Note: The previous algorithm chooser lists AM_RSA_CRT_DECRYPT. This AM will not perform blinding (see “Timing Attacks and Blinding” on page 95). If you want your application to perform blinding, use AM_RSA_CRT_ENCRYPT_BLIND or AM_RSA_CRT_DECRYPT_BLIND.

The Surrender Context

Some Crypto-C functions are time-consuming. When an application calls one of these functions, it can appear as if the computer has crashed or frozen. A lengthy Crypto-C function can tie up the computer, forcing other applications or programs to wait until the Crypto-C function is finished to continue their execution. The surrender context is a way for an application to allow Crypto-C to surrender control.

In general, it is a good idea to include a surrender context whenever a function takes several seconds to execute. The following functions are extremely time-consuming:

•Functions for parameter generation

•Functions for key generation

•Functions for creating acceleration tables

Other functions are less time-consuming and might not need a surrender context in your application. These include many of the block-cipher and stream-cipher symmetric-key operations as well as message digests.

Note: Using a surrender context with private-key operations (such as signing or opening a digital envelope) makes your key more susceptible to a timing attack. You may want to pass in a NULL surrender context for private key operations for security reasons.

The surrender context information is contained in an A_SURRENDER_CTX structure. The file aglobal.h gives the definition; this is described in Chapter 1 of the Reference Manual:

1 1 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