In message <[EMAIL PROTECTED]> on Mon, 03 May 2004 18:15:48 +0000, Carlos Cabaņero
<[EMAIL PROTECTED]> said:
charlychango> I'm giving a look to the code of OpenSSL as I'm very
charlychango> interested in RSA encryptation / decryp. specially for a
charlychango> subject called Discrete Math. My problem is that I have
charlychango> to work on an algorithm by myself and, of course, I'm
charlychango> trying to implement and understand some things that OSSL
charlychango> uses like the Arbitrary Precision Numbers (BIGNUM).
charlychango>
charlychango> What I can't understand is how the function BN_bin2bn
charlychango> works (or at least, I know what it does but I think
charlychango> doesn't do it correctly). For example, imagine that I
charlychango> have to transform the string "1234" to the BIGNUM->d
charlychango> (that it's a pointer to a long):
If the string "1234" is to be interpreted as a hexadecimal number, you
should use BN_hex2bn(). If it's to be interpreted as a decimal
number, you should use BN_dec2bn().
BN_bin2bn() is supposed to be used when you get a number in raw binary
form. If you have the number 1234 stored in a unsigned char array (in
big-endian form, which is required by BN_bin2bn()), then it could look
like this (I trust you understand C enough to understand what this
does):
unsigned char raw_input[] = { 4, 210 }; /* 1234 = 4 * 256 + 210 */
BIGNUM *bn = BN_bin2bn(raw_input, sizeof(raw_input));
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