Re: [opensc-devel] [opensc-commits] svn opensc changed[4930] add to r4904: fix calculating of signature size for CKK_GOSTR3410
Hello, On Dec 9, 2010, at 9:23 AM, webmas...@opensc-project.org wrote: Revision: 4930 Author: s Date: 2010-12-09 07:23:10 + (Thu, 09 Dec 2010) Log Message: --- add to r4904: fix calculating of signature size for CKK_GOSTR3410 - *pLength *= 2; + *pLength = (*pLength + 7) / 8 * 2; Could you also add a comment? Why not (*pLength + 7) / 4? -- @MartinPaljak.net +3725156495 ___ opensc-devel mailing list opensc-devel@lists.opensc-project.org http://www.opensc-project.org/mailman/listinfo/opensc-devel
Re: [opensc-devel] [opensc-commits] svn opensc changed[4930] add to r4904: fix calculating of signature size for CKK_GOSTR3410
On 12/09/2010 11:40 AM, Martin Paljak wrote: Hello, On Dec 9, 2010, at 9:23 AM, webmas...@opensc-project.org wrote: Revision: 4930 Author: s Date: 2010-12-09 07:23:10 + (Thu, 09 Dec 2010) Log Message: --- add to r4904: fix calculating of signature size for CKK_GOSTR3410 -*pLength *= 2; +*pLength = (*pLength + 7) / 8 * 2; Could you also add a comment? Why not (*pLength + 7) / 4? Replying instead of the commit's author. (length + 7) / 8 is a common way to calculate stride width so that the result is aligned to 8. It might be a good idea to give a meaningful name to 2, but please don't simplify the calculation by replacing / 8 * 2 with 4 as it would make it harder to understand. Regards, Kalev ___ opensc-devel mailing list opensc-devel@lists.opensc-project.org http://www.opensc-project.org/mailman/listinfo/opensc-devel
Re: [opensc-devel] [opensc-commits] svn opensc changed[4930] add to r4904: fix calculating of signature size for CKK_GOSTR3410
Hello, 2010/12/9 Martin Paljak mar...@paljak.pri.ee: Hello, On Dec 9, 2010, at 9:23 AM, webmas...@opensc-project.org wrote: Revision: 4930 Author: s Date: 2010-12-09 07:23:10 + (Thu, 09 Dec 2010) Log Message: --- add to r4904: fix calculating of signature size for CKK_GOSTR3410 - *pLength *= 2; + *pLength = (*pLength + 7) / 8 * 2; Could you also add a comment? Why not (*pLength + 7) / 4? Yes of course. We need to convert a length in bits to bytes and multiply by two. So if we divide by 4 then we have incorrect rounding result (case (*pLength + 7) % 8 = 4). ___ opensc-devel mailing list opensc-devel@lists.opensc-project.org http://www.opensc-project.org/mailman/listinfo/opensc-devel
Re: [opensc-devel] [opensc-commits] svn opensc changed[4930] add to r4904: fix calculating of signature size for CKK_GOSTR3410
On Thu, 2010-12-09 at 14:31 +0300, Aleksey Samsonov wrote: Hello, 2010/12/9 Martin Paljak mar...@paljak.pri.ee: Hello, On Dec 9, 2010, at 9:23 AM, webmas...@opensc-project.org wrote: Revision: 4930 Author: s Date: 2010-12-09 07:23:10 + (Thu, 09 Dec 2010) Log Message: --- add to r4904: fix calculating of signature size for CKK_GOSTR3410 - *pLength *= 2; + *pLength = (*pLength + 7) / 8 * 2; Could you also add a comment? Why not (*pLength + 7) / 4? Yes of course. We need to convert a length in bits to bytes and multiply by two. So if we divide by 4 then we have incorrect rounding result (case (*pLength + 7) % 8 = 4). Maybe it would be appropriate to define a macro for the conversion. The Reason is, that there are a lot of places where the conversion is computed as follows: byte_count = bit_count / 8. That is obviously wrong in 7 of 8 cases. Also it would improve readability. Regards Andre ___ opensc-devel mailing list opensc-devel@lists.opensc-project.org http://www.opensc-project.org/mailman/listinfo/opensc-devel
Re: [opensc-devel] [opensc-commits] svn opensc changed[4930] add to r4904: fix calculating of signature size for CKK_GOSTR3410
On Thu, 2010-12-09 at 09:38 -0600, Douglas E. Engert wrote: On 12/9/2010 8:41 AM, Andre Zepezauer wrote: On Thu, 2010-12-09 at 14:31 +0300, Aleksey Samsonov wrote: Hello, 2010/12/9 Martin Paljakmar...@paljak.pri.ee: Hello, On Dec 9, 2010, at 9:23 AM, webmas...@opensc-project.org wrote: Revision: 4930 Author: s Date: 2010-12-09 07:23:10 + (Thu, 09 Dec 2010) Log Message: --- add to r4904: fix calculating of signature size for CKK_GOSTR3410 - *pLength *= 2; + *pLength = (*pLength + 7) / 8 * 2; Could you also add a comment? Why not (*pLength + 7) / 4? Yes of course. We need to convert a length in bits to bytes and multiply by two. So if we divide by 4 then we have incorrect rounding result (case (*pLength + 7) % 8= 4). Maybe it would be appropriate to define a macro for the conversion. The Reason is, that there are a lot of places where the conversion is computed as follows: byte_count = bit_count / 8. That is obviously wrong in 7 of 8 cases. Also it would improve readability. It may comes down to does an algorthim support non-multiple of 8 bits? And if it can, is it ever used with non multiple of 8 bits? I have never sees an RSA key that was not a multiple of 8, so it may not be an issue for most of OpenSC. If one is not a multiple of 8, how is it padded? At least for RSA_PKCS1 the most significant octet is always zero. See PKCS1 01- and 02-padding schema. Therefore the padded signature input is always less than the modulus when compared numerical. ___ opensc-devel mailing list opensc-devel@lists.opensc-project.org http://www.opensc-project.org/mailman/listinfo/opensc-devel
