5812-DS01-R datasheet(35/84 Pages) BOARDCOM

35 / 84 page

Advance Data Sheet

BCM5812

3/11/03

B roa dcom Co rpo rat ion

Document

5812-DS01-405-R

Cryptographic Operations

Page 27

The modulus and generator lengths can be between 16 and 2048 bits, and are specified in bits in the command context. The

modulus and generator fields in the command context must take on one of the parameter field sizes in Table 10.

The exponent length is specified in bits in the command context. The BCM5812 can use its internal random number

generator to generate a new secret value of length exponent length if generate secret is equal to 0x0001. If generate secret

is equal to 0x0000, the host software must supply an exponent length input secret, as a BigNum, using the appropriate

parameter size increment. Generate secret should be one of these two values.

Figure 25 illustrates the layout of a BigNum argument. A modulus or generator that is less than the parameter field size must

start with its least significant bit in the first 32-bit word, and be padded with zeros to the parameter field size in its high order

bits.

Note

The BCM5812 interprets all large integer arguments as “BigNums,” arrays of 32-bit “digits” ordered

least significant digit first. That is, the digit containing the least significant bit of the large integer is at

the lowest ordered index in the array.

Table 10: Allowed Public Key Parameter Field Size Increments

Modulus Length, in Bits

Parameter Size in 32-bit words

Parameter SIze in Bytes

16-512

513-768

769-1024

128

1025-1536

192

1537-2048

256

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