// COMPLETE THREAD

Question about Blind Signature

2 expanded posts · every known parent and child

NODE 5b9e575eQuestion about Blind Signature Chein-hsinLiu <r3506010@cml11.csie.ntu.edu.tw>Thu, 28 Mar 96 05:19:10 PST

Hi!
I have some stupid question about how to implement blind signature.
I Know it works as follows:
If A wants B to sign X but donot know it is X, A can send
   X*PK(random)  : PK is public key of B
Then B signs on message:
  SK(X*PK(random)) ==> SK(X)*random
Then A can obtain SK(X) by SK(X)*random/random

My question is when I see how RSA encrypts using PKCS
The PKCS block is like this
 00 01 FF FF FF FF ... 00 input
Then SK(00 01 FF FF FF .. 00 input) .
If the input = X*PK(random)
then SK(00 01 FF FF FF .. 00 X*PK(random)) will not produce SK(X)*random
How to solve this??
Thanks!!

NODE 4c29b35fRe: Question about Blind Signature Derek Atkins <warlord@MIT.EDU>Thu, 28 Mar 96 08:09:37 PST

> My question is when I see how RSA encrypts using PKCS
> [desc. deleted]
> How to solve this??

You don't.  Blind signatures only work with "pure" RSA.  You cannot
use PKCS encoding to perform blind signatures.  PKCS nullifies the
multiplicity that is required for these blinding techniques to work.

-derek