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The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:18:33 ADT
Teh Kao Yang (tehyang@gate.infoexpress.com)
Tue, 16 Jun 1998 16:27:01 -0700
Hi there,
THanks for the reply. Yes I understand that most of the time you
encrypt with a symmetric session key.. but I guess I didn't really
state my problem clearly enough.. what I really needed was to be able
to sign some data with a RSA private key. Now I've been able to find
libraries that, given some data, will hash the data and then sign
the hash. The thing this, I couldn't find any thing that will just
do the signing and not the hashing as well. For example RSAREF does
provide hashing+signing composite functions... what I need is just
the signing/encrypting part... I already have a hashed value available.
I tried the Microsoft Crypto API, and that had a function that sort of
does this, because you can provide a pre-hashed data for it to sign... but
the problem is, it only accepts pre-hashed data in 16, 20 , or 30 byte
lengths (I guess corresponding to MD5, and SHA). It will not sign an
arbritraly length of data.
Ok sorry if this is getting too long, but I guess I still haven't really
explained what I need this function for. I am trying to do a PKCS#1
digital signature. In PKCS#1 they define that you have to first has
h the data, then DER encode the hash, then encrypt with RSA. Now what
I have (all I have) is the DER encoded hash... I need a pure RSA encrypt
function that will hash this data... which is exactly 34 bytes in length.
Ok there is also the matter of padding the hash so that the length matches
the modulus of the private key, but I can take care of that.
Anyways, sorry for dragging out the explanation like this... but I was
just trying to explain my dilemma more clearly...
Thanks
TK
The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:18:33 ADT