RSA Security Projection Television 5.2.2 Manual de usuario descargar pdf (Pagina 207)

Chapter 6 Symmetric-Key Operations 185

Block Ciphers

Once again,

encryptionMethodName

is the block cipher that you will use; in this

example, use

“rc2”. All the other parameters are the same as for DES, except

encryptionParams

. For the RC2 cipher, the Reference Manual indicates that you need to

supply an

A_RC2_PARAMS structure for the RC2 encryption algorithm:

There is a distinction between key size and effective key bits. The RC2 algorithm

begins by building a 128-byte table based on the key. The total number of possible

tables is limited by the number of effective key bits. Using 80 effective key bits is

generally sufficient for most applications.

Use Cipher Block Chaining (CBC) for your feedback method. Once again, for this

method, you need an initialization vector; use a random number generator to produce

one. Remember, the IV is not secret and will not assist anyone in breaking the

encryption. Its size will be eight bytes, because the RC2 cipher encrypts blocks of eight

bytes. The Reference Manual says that

feedbackParams

is an ITEM structure containing

the initialization vector:

Now you can set your algorithm object as follows:

typedef struct {

unsigned int effectiveKeyBits; /* effective key size in bits */

} A_RC2_PARAMS;

typedef struct {

unsigned char *data;

unsigned int len;

} ITEM;

ITEM ivItem;

unsigned char initVector[BLOCK_SIZE];

A_RC2_PARAMS rc2Params;

B_BLK_CIPHER_W_FEEDBACK_PARAMS fbParams;

/* Complete steps 1 - 4 of Generating Random Numbers,

then call B_GenerateRandomBytes. */

if ((status = B_GenerateRandomBytes

(randomAlgorithm, (unsigned char *)initVector, 8,

(A_SURRENDER_CTX *)NULL_PTR)) != 0)

break;

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RSA Security Projection Television 5.2.2 Manual de usuario Pagina 207