Re: RSA_private_encrypt

[Montini Paolo]

Thanks very much for the suggestion. It is not enough to free and null rsa->p, rsa->q, rsa->dmp1 and rsa->dmq1. You have also to set them with new values such as :         ctx = BN_CTX_new();     BN_clear(rsa->d);     rsa->d = BN_copy((BIGNUM*)rsa->d, (const BIGNUM*)new_privkey);      err = BN_mod(rsa->dmp1, rsa->d, rsa->p, ctx);   And then it will work ! The problem now is that if I sign a message digest (using RSA_sign()) after these operations, then RSA_verify fails, because the padding check fails !   Even if I replace the rsa->d with the same one generated by RSA_generate_key and stoerd in new_privkey with BN_copy, the RSA_verify fails !   I think that there is something wrong with the RSA structure, but I have no idea of what I can do to make it working !   Does anybody have any idea ? Thanks again, Paolo. ----- Original Message ----- From: SCH To: [EMAIL PROTECTED] Sent: Sunday, September 17, 2000 5:50 PM Subject: Re: RSA_private_encrypt To change a RSA private key, you should manually change the rsa->d,  and clear (free and set to NULL) the rsa->p, rsa->q, rsa->dmp1, rsa->dmq1, and rsa->iqmp, because they are also generated in the RSA_generate_key() , and if they are generated, the computation will use them, not use the 'd' directly. It is a faster computation. To gain a private key you want, the nicer practise is set the e as you want. ----- Original Message ----- From: Dr S N Henson <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, September 16, 2000 4:15 AM Subject: Re: RSA_private_encrypt > "montinip@libero." wrote: > > > > Hi everybody, > > I have a problem: I am developing a project in which I need to use > > 'special' RSA private keys. > > I use RSA_generate_key() to generate the key pair and the I use BN_copy > > to modify manually tha value of rsa->d. > > If I check with RSA_check_key the test fails as it was supposed to do > > and also I am sure that the value has been changed when I use RSA_print! > > But when I use RSA_private_encrypt to sign a digest it uses the 'old' > > rsa->d value, the one generated with RSA_generate_key !!! > > > > Someone can tell me why? How does RSA_private_encrypt work?Why it > > doesn't simply do to = from^rsa->d mod rsa->n ? > > > > It doesn't do that because it uses the Chinese remainder theorem > version of the RSA algorithm which is faster. > > The reason you are seeing that behaviour is that the CRT version > doesn't use 'd' if all the other CRT components are present. Try > BN_free()ing and NULLing one or more of the components like rsa->p > or rsa->q first. > > Steve. > -- > Dr Stephen N. Henson.   http://www.drh-consultancy.demon.co.uk/ > Personal Email: [EMAIL PROTECTED] > Senior crypto engineer, Celo Communications: http://www.celocom.com/ > Core developer of the   OpenSSL project: http://www.openssl.org/ > Business Email: [EMAIL PROTECTED] PGP key: via homepage. > ______________________________________________________________________ > OpenSSL Project                                 http://www.openssl.org > Development Mailing List                       [EMAIL PROTECTED] > Automated List Manager                           [EMAIL PROTECTED] ______________________________________________________________________ OpenSSL Project                                 http://www.openssl.org Development Mailing List                       [EMAIL PROTECTED] Automated List Manager                           [EMAIL PROTECTED]