RSA Security Projection Television 5.2.2 Instrukcja Użytkownika Pobierz pdf (Strona 267)

Chapter 7 Public-Key Operations 245

Performing DSA Operations

properly cast NULL_PTR for the surrender context:

Step 4: Update

Digest the data to sign with B_SignUpdate, the prototype of which is in Chapter 4 of

the Reference Manual. Unless there is an extraordinarily large amount of data (for

example, a megabyte or more), this function is quick and a

NULL_PTR for the surrender

context should be no problem. Assuming you have some input data and you know its

length, your call is the following:

Step 5: Final

B_SignUpdate digested the data. Create the signature and send the result to a

signature buffer with

B_SignFinal. The signature will be as many as 48 bytes long, so

make sure the output buffer is big enough. The Reference Manual Chapter 2 entry on

AI_DSAWithSHA1 states:

This function does not return immediately, so a surrender context can be helpful. For

this example, use the surrender context described in “The Surrender Context” on

B_ALGORITHM_METHOD *DSA_SIGN_CHOOSER[] = {

&AM_SHA,

&AM_DSA_SIGN,

(B_ALGORITHM_METHOD *)NULL_PTR

};

if ((status = B_SignInit

(dsaSigner, dsaPrivateKey, DSA_SIGN_CHOOSER,

(A_SURRENDER_CTX *)NULL_PTR)) != 0)

break;

if ((status = B_SignUpdate

(dsaSigner, inputData, inputDataLen,

(A_SURRENDER_CTX *)NULL_PTR)) != 0)

break;

You must pass a random algorithm in B_SignFinal, but may pass

(B_ALGORITHM_OBJ)NULL_PTR for all other

randomAlgorithm

arguments.

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RSA Security Projection Television 5.2.2 Instrukcja Użytkownika Strona 267