Difference between revisions of "Cryptography"

From Hackepedia
Jump to: navigation, search
m
m (Reverted edits by IoqNk6 (Talk); changed back to last version by Hawson)
Line 1: Line 1:
[[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=107 music ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=185 zoloft online]] [[http://wc1.worldcrossing.com/WebX/.1de609f1 lortab online]] [[http://wc1.worldcrossing.com/WebX/.1de60a2e cheap xanax]] [[http://wc1.worldcrossing.com/WebX/.1de60a0b cheap vigrx]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30297 cheap albuterol]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30361 kyocera ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=103 free mono ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=97 cheap lipitor]] [[http://library.cshl.edu/wp/vb/member.php?u=1366 buy propecia]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=155 xanax online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=177 propecia online]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=85 ericsson ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609fb ortho online]] [[http://wc1.worldcrossing.com/WebX/.1de609ec buy hgh]] [[http://library.cshl.edu/wp/vb/member.php?u=1370 tracfone ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609e3 clomid online]] [[http://wc1.worldcrossing.com/WebX/.1de60a29 tramadol online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2889 cheap vigrx]] [[http://wc1.worldcrossing.com/WebX/.1de60a18 free motorola ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=121 real ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=162 order meridia]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2886 ortho online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=213 free polyphonic ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=135 ultracet online]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30335 nextel ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2881 cheap lisinopril]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=241 sony ericsson ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=128 free sony ericsson ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2916 free alltel ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2897 free nokia ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a0f cialis online]] [[http://wc1.worldcrossing.com/WebX/.1de60a09 viagra online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=207 free real ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a0e cheap celexa]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=229 valium online]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=354 free nokia ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2866 cheap levitra]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=200 nokia ringtones]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=200 nexium]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=214 cingular ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2910 polyphonic ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2891 diethylpropion online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2885 order tenuate]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=159 cialis online]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30366 free jazz ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609fa online pharmacy]] [[http://wc1.worldcrossing.com/WebX/.1de60a22 but phentermine]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=208 motorola ringtones]] [[http://library.cshl.edu/wp/vb/member.php?u=1357 levitra online]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=195 free mono ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=199 zyban online]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=363 samsung ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2901 mp3 ringtones]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30235 cheap soma]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=136 ultram online]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=72 ambien online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2862 buy vicodin]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30258 vicodin online]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=182 funny ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2890 zanaflex]] [[http://wc1.worldcrossing.com/WebX/.1de609dc albuterol online]] [[http://wc1.worldcrossing.com/WebX/.1de60a20 nexium online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2875 buy propecia]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=165 ambien]] [[http://wc1.worldcrossing.com/WebX/.1de609f8 free nokia ringtones]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=350 alprazolam]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=139 cheap viagra]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2874 cheap ultracet]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=91 hoodia online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=175 cyclobenzaprine online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=201 free free ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=153 phentermine online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2848 soma online]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30337 real ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=94 free jazz ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a0a vicodin]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2896 buy zyban]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=178 free ericsson ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a01 free sagem ringtones]] [[http://library.cshl.edu/wp/vb/member.php?u=1346 diazepam online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=222 sharp ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a1d cingular ringtones]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30230 but adipex]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=138 verizon ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609fe free qwest ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609e4 cheap clonazepam]] [[http://wc1.worldcrossing.com/WebX/.1de60a31 buy zanaflex]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=106 free mtv ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a1a mtv ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a15 kyocera ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=218 sony ericsson ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=132 tenuate online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2904 free real ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=137 cheap valium]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=168 cheap paxil]] [[http://library.cshl.edu/wp/vb/member.php?u=1367 didrex online]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30295 sildenafil online]] [[http://wc1.worldcrossing.com/WebX/.1de609f7 nextel ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609f3 free midi ringtones]] [[http://library.cshl.edu/wp/vb/member.php?u=1348 ativan online]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=337 xanax online]] [[http://wc1.worldcrossing.com/WebX/.1de609e6 cyclobenzaprine online]] [[http://library.cshl.edu/wp/vb/member.php?u=1360 lorazepam online]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=162 alltel ringtones]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=176 cheap didrex]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=204 free mp3 ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2911 cingular ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a07 free tracfone ringtones]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30241 xanax online]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=356 free tracfone ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=111 order norco]] [[http://wc1.worldcrossing.com/WebX/.1de60a13 fioricet online]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=191 lorazepam online]] [[http://library.cshl.edu/wp/vb/member.php?u=1369 free free ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2858 viagra online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=224 wwe ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2852 buy xanax]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30307 cheap zoloft]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30331 free ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a27 but sildenafil]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=145 xenical online]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30339 free samsung ringtones]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30294 prozac online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=176 ultracet online]] [[http://library.cshl.edu/wp/vb/member.php?u=1352 buy norco]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=189 lipitor]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=362 free motorola ringtones]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=224 sagem ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=101 buy meridia]] [[http://wc1.worldcrossing.com/WebX/.1de609ee but hydrocodone]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30244 diazepam online]] [[http://wc1.worldcrossing.com/WebX/.1de609e0 ativan online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2861 cheap norco]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2877 cheap prozac]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=216 free sonyericsson ringtones]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=360 qwest ringtones]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=190 cheap lisinopril]] [[http://wc1.worldcrossing.com/WebX/.1de60a10 cheap didrex]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=228 ultram online]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=76 online cialis]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30259 cheap alprazolam]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=359 free nextel ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609e5 free cool ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2888 cheap lortab]] [[http://library.cshl.edu/wp/vb/member.php?u=1373 nextel ringtones]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=216 zyban online]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=206 cheap pharmacy online]] [[http://library.cshl.edu/wp/vb/member.php?u=1344 cheap xanax]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=344 ativan]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30345 free sprint ringtones]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30248 ativan online]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=131 sprint ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2871 wellbutrin online]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=146 zanaflex online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=154 carisoprodol online]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30280 cheap propecia]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=118 prozac online]] [[http://library.cshl.edu/wp/vb/member.php?u=1341 valium online]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=144 cheap xanax]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2905 motorola ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=112 but ortho]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=223 cheap wellbutrin]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=169 levitra online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=156 online fioricet]] [[http://library.cshl.edu/wp/vb/member.php?u=1377 samsung ringtones]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30312 cheap ortho]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30356 cool ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609f0 lorazepam online]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=187 cheap celexa]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30230 tramadol online]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=211 polyphonic ringtones]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=214 cheap zanaflex]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=110 free nokia ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=189 cheap ortho]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=237 free samsung ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=151 order soma]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=99 cheap lorazepam]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2912 sagem ringtones]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2907 sprint ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a17 lipitor online]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30334 free mp3 ringtones]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=234 sprint ringtones]] [[http://www.ees.ufl.edu/alumni/forums.asp?ForumId=5&TopicId=141 buy vigrx]] [[http://wc1.worldcrossing.com/WebX/.1de60a23 polyphonic ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de60a1f lisinopril online]] [[http://itcweb.ecsu.edu/portal/forums.asp?ForumId=13&TopicId=197 free mp3 ringtones]] [[http://library.cshl.edu/wp/vb/member.php?u=1349 viagra online]] [[http://library.cshl.edu/wp/vb/member.php?u=1382 cingular ringtones]] [[http://www.e.kth.se/cgi-bin/esekt/discussion?command=read&discussionid=4&id=30310 tenuate online]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2922 kyocera ringtones]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=206 free qwest ringtones]] [[http://wc1.worldcrossing.com/WebX/.1de609f9 cheap norco]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=351 buy clonazepam]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2878 cheap sildenafil]] [[http://students.hsc.unt.edu/housing/item.cfm?type=2902 free nextel ringtones]] [[http://www.psfc.mit.edu/~jinseok/bbse/view.php?id=presentations&no=357 funny ringtones]] [[http://library.cshl.edu/wp/vb/member.php?u=1347 but cialis]] [[http://library.cshl.edu/wp/vb/member.php?u=1365 cheap ultracet]] [[http://news.engin.brown.edu/forums/thread-view.asp?tid=210 free sprint ringtones]] Cryptography is the method for distorting plain text so that it is unreadable by someone other than the intended recipient.  For example, someone that is using a packet [[sniffer]] to listen in on network communication.  Only if this third party knows the secret key to the ciphertext will they break the encryption and be able to see the plaintext. We highly recommend anyone using plain text protocols these days to use their free, open source, encrypted equivalents.
+
Cryptography is the method for distorting plain text so that it is unreadable by someone other than the intended recipient.  For example, someone that is using a packet [[sniffer]] to listen in on network communication.  Only if this third party knows the secret key to the ciphertext will they break the encryption and be able to see the plaintext. We highly recommend anyone using plain text protocols these days to use their free, open source, encrypted equivalents.
  
 
=== Cryptography found in UNIX ===
 
=== Cryptography found in UNIX ===
Line 5: Line 5:
  
 
=== One way hashing ===
 
=== One way hashing ===
UNIX programmers implemented a [[One way hash]] of [[DES]] to "encrypt" [[password]]s as part of the crypt(3) function.  It was impossible to decrypt these [[password]]s since they were a modified version of DES, so in order to know if someone had the right [[password]] the plain text would be encrypted and the result compared with the hash of the password database. If they matched, a user would be granted access. As computers became faster so did the speed at which DES would be cracked.  An amd64 3500 running [[OpenBSD]] using the systems crypt(3) functions can hash 121,000 [[password]]s in 1 second in 2005.  So a slower hash algorithm was needed and one that could take more than 8 characters for the [[password]]s.  Many Operating Systems have implemented [[MD5]] hashing which does 1880 crypts per second on the aforementioned OpenBSD system.  OpenBSD went even further and designed an interesting hash of [[blowfish]] that has a variable setting for rounds that blowfish will encrypt the hash with the string "OrpheanBeholderScryDoubt" 64 times per round.  The result is that with 12 rounds, a crypt will do 2 passwords in 1 second.
+
UNIX programmers implemented a [[One way hash]] of [[DES]] to "encrypt" [[password]]s as part of the crypt(3) function.  It was impossible to decrypt these [[password]]s since they were a modified version of DES, so in order to know if someone had the right [[password]] the plain text would be encrypted and the result compared with the hash of the password database. If they matched, a user would be granted access. As computers became faster so did the speed at which DES would be cracked.  An amd64 3500+ running [[OpenBSD]] using the systems crypt(3) functions can hash 121,000 [[password]]s in 1 second in 2005.  So a slower hash algorithm was needed and one that could take more than 8 characters for the [[password]]s.  Many Operating Systems have implemented [[MD5]] hashing which does 1880 crypts per second on the aforementioned OpenBSD system.  OpenBSD went even further and designed an interesting hash of [[blowfish]] that has a variable setting for rounds that blowfish will encrypt the hash with the string "OrpheanBeholderScryDoubt" 64 times per round.  The result is that with 12 rounds, a crypt will do 2 passwords in 1 second.
  
 
[[One way hash]]ing wasn't confined to just passwords. With the [[md5]] and [[SHA]], as well as the [[rmd160]] commands one can make a cryptographic hash sum (or fingerprint) of a file or text in the system. For example, if you want to ensure a file or directory has not been altered, you can print the checksum onto read-only media (i.e. paper/burn onto a cd). Whenever you run the checksum program against the same file or directory, you should get the same results unless something has been altered. If this topic interests you, [http://sourceforge.net/projects/tripwire/ tripwire] is popular software you'll want to read more about.
 
[[One way hash]]ing wasn't confined to just passwords. With the [[md5]] and [[SHA]], as well as the [[rmd160]] commands one can make a cryptographic hash sum (or fingerprint) of a file or text in the system. For example, if you want to ensure a file or directory has not been altered, you can print the checksum onto read-only media (i.e. paper/burn onto a cd). Whenever you run the checksum program against the same file or directory, you should get the same results unless something has been altered. If this topic interests you, [http://sourceforge.net/projects/tripwire/ tripwire] is popular software you'll want to read more about.
Line 39: Line 39:
  
 
  $ cat /etc/passwd | ./xortext blah | hexdump -C | head
 
  $ cat /etc/passwd | ./xortext blah | hexdump -C | head
  00000000  10 03 0e 1c 58 46 5b 58  58 5c 5b 2b 0a 0d 13 04  |....XF[XX\[ ....|
+
  00000000  10 03 0e 1c 58 46 5b 58  58 5c 5b 2b 0a 0d 13 04  |....XF[XX\[+....|
 
  00000010  0b 09 41 4e 4e 40 4d 52  4d 1e 0e 07 16 56 4e 0a  |[email protected]|
 
  00000010  0b 09 41 4e 4e 40 4d 52  4d 1e 0e 07 16 56 4e 0a  |[email protected]|
 
  00000020  0b 02 4e 1b 0a 66 05 09  07 01 0e 06 58 46 5b 59  |..N..f......XF[Y|
 
  00000020  0b 02 4e 1b 0a 66 05 09  07 01 0e 06 58 46 5b 59  |..N..f......XF[Y|

Revision as of 05:53, 16 July 2007

Cryptography is the method for distorting plain text so that it is unreadable by someone other than the intended recipient. For example, someone that is using a packet sniffer to listen in on network communication. Only if this third party knows the secret key to the ciphertext will they break the encryption and be able to see the plaintext. We highly recommend anyone using plain text protocols these days to use their free, open source, encrypted equivalents.

Cryptography found in UNIX


One way hashing

UNIX programmers implemented a One way hash of DES to "encrypt" passwords as part of the crypt(3) function. It was impossible to decrypt these passwords since they were a modified version of DES, so in order to know if someone had the right password the plain text would be encrypted and the result compared with the hash of the password database. If they matched, a user would be granted access. As computers became faster so did the speed at which DES would be cracked. An amd64 3500+ running OpenBSD using the systems crypt(3) functions can hash 121,000 passwords in 1 second in 2005. So a slower hash algorithm was needed and one that could take more than 8 characters for the passwords. Many Operating Systems have implemented MD5 hashing which does 1880 crypts per second on the aforementioned OpenBSD system. OpenBSD went even further and designed an interesting hash of blowfish that has a variable setting for rounds that blowfish will encrypt the hash with the string "OrpheanBeholderScryDoubt" 64 times per round. The result is that with 12 rounds, a crypt will do 2 passwords in 1 second.

One way hashing wasn't confined to just passwords. With the md5 and SHA, as well as the rmd160 commands one can make a cryptographic hash sum (or fingerprint) of a file or text in the system. For example, if you want to ensure a file or directory has not been altered, you can print the checksum onto read-only media (i.e. paper/burn onto a cd). Whenever you run the checksum program against the same file or directory, you should get the same results unless something has been altered. If this topic interests you, tripwire is popular software you'll want to read more about.

Symmetric cryptography

True private key cryptography was also present with the bdes and the openssl commands which could encrypt files with a variety of ciphers. Some well known ciphers are DES, AES, blowfish, CAST128 and Arcfour. Many ciphers are imported through the openssl library.


Public Key cryptography

Also called assymetric cryptography. It uses 2 or more keys, usually one that's private and one that's public which is publically known. Ciphers include Diffie Hellman (DH), and RSA. GPG a program to encrypt mail on the application OSI layer uses this.


Symmetric / Assymmetric Hybrids

This method is used in OSI session layer communication. A public-key exchange takes place to agree on a session key which is random and also a Symmetric encryption and all data following will be encrypted. This is used extensively in ssh and most SSL enabled software.


Cheap cryptography

Rotational Ciphers based on the alphabet are CHEAP. Often used by Usenet trolls who think that the people they troll don't have a clue what they are talking about.

$ echo OrpheanBeholderScryDoubt | /usr/games/rot13
BecurnaOrubyqreFpelQbhog

rot13 is probably good to keep data safe from your 7 year old sister.

Another type of cryptography is the XOR method. XOR used as a One time pad is potentially secure. Here is an example of a typical XOR encryption the xortext.c program is also available:

$ cat /etc/passwd | ./xortext blah | hexdump -C | head
00000000  10 03 0e 1c 58 46 5b 58  58 5c 5b 2b 0a 0d 13 04  |....XF[XX\[+....|
00000010  0b 09 41 4e 4e 40 4d 52  4d 1e 0e 07 16 56 4e 0a  |[email protected]|
00000020  0b 02 4e 1b 0a 66 05 09  07 01 0e 06 58 46 5b 59  |..N..f......XF[Y|
00000030  58 5d 5b 3c 0a 09 41 0c  07 1a 08 04 42 04 08 05  |X][<..A.....B...|
00000040  11 09 0d 0e 58 43 13 07  0d 18 5b 47 11 0e 08 06  |....XC....[G....|
00000050  4d 02 0e 04 0d 0b 08 06  68 03 11 0d 10 0d 15 07  |M.......h.......|
00000060  10 56 4b 52 50 56 54 52  31 15 12 1c 07 01 41 4e  |.VKRPVTR1.....AN|
00000070  58 43 0e 18 07 1e 00 1c  0d 1e 5b 47 11 0e 08 06  |XC........[G....|
00000080  4d 02 0e 04 0d 0b 08 06  68 0e 08 06 58 46 5b 5b  |M.......h...XF[[|
00000090  58 5b 5b 2a 0b 02 00 1a  0b 09 12 48 21 03 0c 05  |X[[*.......H!...|

Surprisingly some companies employ XOR cryptography in their products as a secruity mechanism.