see below > -----Ursprüngliche Nachricht----- > Von: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Auftrag von Tan Eng Ten > Gesendet: Mittwoch, 17. August 2005 11:28 > An: openssl-users@openssl.org > Betreff: Re: AW: RSA key sizes > > > Cool.. but the key below has 128 bytes in total, but reported > as being > 1023-bit
Because it only consits of 1023 bit and a leading zero... which is not counted. > > ----- > Modulus (1023 bit): > 5d:10:63:d3:d8:00:2a:50:ab:65:8a:f0:92:83:b0: > 6a:39:e3:0c:38:aa:f5:32:23:71:25:8e:4a:8d:50: > fd:80:a3:95:59:33:27:92:88:d0:1d:28:dd:05:7c: > b6:a0:5e:68:9e:b4:70:c9:bd:28:8a:fb:6d:95:0a: > 38:83:f9:8d:15:b1:3a:33:bf:d7:ab:1c:5e:1b:d3: > d6:c1:1a:f8:05:7f:ef:22:23:48:ef:48:a2:8d:99: > 90:10:81:8a:54:dd:16:9e:7f:d0:88:a8:b7:34:68: > be:4d:8f:dc:4b:5d:d9:72:c5:a4:88:a6:40:fa:f2: > f7:16:79:a8:35:3d:f2:ad > Exponent: 3 (0x3) > ----- > > I notice that for 1024-bit RSA key generated by openssl, the > modulus has > 129 bytes but having the first byte = 0. Why is this?, for example: This is correct because in BER a leading "1" tells you, that this is a negativ integer. But while we are working with positve integer we have to add at least one leading "0"... so we have to add one byte. > > ----- > Modulus (1024 bit): > 00:d8:6e:77:67:5e:29:bb:4e:83:52:fe:fa:fc:58: > 04:d8:07:3e:43:11:92:10:45:dc:f2:f7:7a:77:49: > 91:cf:cc:0d:5e:ec:d9:44:15:2d:61:19:cd:9d:79: > 9e:27:80:61:6c:a3:db:34:21:cf:87:60:7a:e4:d9: > a5:02:59:57:fb:4e:8c:e4:32:fb:5e:cb:1a:99:7b: > 76:b2:79:ae:2f:1f:62:1d:f6:fc:9e:32:e5:bd:46: > 8f:c7:05:63:aa:10:2c:be:60:46:4a:44:c5:63:94: > b1:ab:d5:c5:33:cd:d7:69:f0:2b:36:54:dd:82:92: > 66:6c:0d:50:81:a1:23:79:67 > Exponent: 65537 (0x10001) > ----- > > > [EMAIL PROTECTED] wrote: > > The main reason why we take 512, 768, 1024, 2048, 4096,... > bit is, that > > these numbers are multiples of 8 ans though can be > fractioned into bytes > > (1024 bit = 128 byte). > > Withe the increase of calculation power the key size was > increased, in the > > end by doubling the number of bits. > > > > To answer our second question: A real 1024-bit-key must > have at least 1017 > > bit, so it consits of 128 byte (= 1024 bit) with 7 leading zeros. > > > > Regards > > > > Thomas Beckmann > > > > > >>-----Ursprüngliche Nachricht----- > >>Von: [EMAIL PROTECTED] > >>[mailto:[EMAIL PROTECTED] Auftrag von Tan Eng Ten > >>Gesendet: Mittwoch, 17. August 2005 08:22 > >>An: openssl-users@openssl.org > >>Betreff: RSA key sizes > >> > >> > >>Hi all, > >> > >> This is a general crypto question and I hope someone > >>could help me out. > >> > >> Often we use RSA of 512, 1024, 2048, 4096, etc. bit > >>lengths. Are other > >>sizes such as 520/1045 bit "valid"? Mathematically, it should > >>work, but > >>are there reasons why odd sizes are not to be used? > >>____________________________________________________________ > __________ > >>OpenSSL Project http://www.openssl.org >>User Support Mailing List openssl-users@openssl.org >>Automated List Manager [EMAIL PROTECTED] >> > > ______________________________________________________________________ > OpenSSL Project http://www.openssl.org > User Support Mailing List openssl-users@openssl.org > Automated List Manager [EMAIL PROTECTED] > > ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager [EMAIL PROTECTED] ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager [EMAIL PROTECTED]
