randinitializebbs() - 5.2 English - 68552

Alternative initialisation routine for the Blum-Blum-Shub generator.

Parameters:

• nbits – [in]

  The number of bits to use from each iteration

  if

  nbits < 1, then nbits = 1

  ,

  if

  nbits > 15, then nbits = 15 (i.e. between 1 and 15 bits can be used)

• lp – [in] The number of digits in the first prime p, lp <= 25

• p – [in]

  The first prime value

  This integer is stored in an array.

  Each element of the array is a digit, and the integer is stored

  base B2, where B2 = 2**30, i.e.

  p = p(1) + p(2)*B2 + p(3)*B2**2 + … + p(lp)*B2**(lp-1), p(lp).

  p mod 4 = 3

• lq – [in] The number of digits in the second prime q, lq <= 25

• q – [in]

  The first prime value

  This integer is stored in an array.

  Each element of the array is a digit, and the integer is stored

  base B2, where B2 = 2**30, i.e.

  q = p(1) + q(2)*B2 + q(3)*B2**2 + … + q(lq)*B2**(lq-1), q(lq).

  q mod 4 = 3

• ls – [in] The number of digits in the initial state s, ls <= 25

• s – [in]

  The first prime value

  This integer is stored in an array.

  Each element of the array is a digit, and the integer is stored

  base B2, where B2 = 2**30, i.e.

  s = s(1) + s(2)*B2 + s(3)*B2**2 + … + s(lp)*B2**(ls-1), s(ls).

• state – [out]

  Array holding information about the generator:

  1 = Amount of state used = 310

  2 = ‘Magic’ number = 5010

  3 = GENID

  4 = SUBID (the number of bits to use)

  5 = PN, the location in state of N

  6 = PX, the location in state of X

  PX = LX, the number of digits of X

  PX+1 to PX+LX = The digits of X

  PN+1 to PN+LN = The digits of N

  310 = ‘Magic’ number = 5010

• lstate – [inout] Length of array state, lstate >= If lstate < 1, then lstate is set to 310 and the function returns.

• info – [out]

  Error code

  1 = Everything OK, but generator not initialized (returned when values of LSEED or lstate given)

  0 = Everything OK

  -1 to -8 = Error in parameter, abs(info).