explain xkcd - User contributions [en]

1286: Encryptic

2013-11-05T13:54:54Z

Qistoph:

{{comic
| number = 1286
| date = November 4, 2013
| title = Encryptic
| image = encryptic.png
| titletext = It was bound to happen eventually. This data theft will enable almost limitless [xkcd.com/792]-style password reuse attacks in the coming weeks. There's only one group that comes out of this looking smart: Everyone who pirated Photoshop.
}}

==Explanation==
Web sites and other computers that authenticate users via passwords need to be able to know if the user typed in the right password. But storing the password itself on the computer has been known to be unnecessarily risky since the publication of [http://www.neurosecurity.com/articles/security/passwd.pdf Password Security: A Case History] in 1978. In that paper, Robert Morris and Ken Thompson demonstrated the practice of using a slow, cryptographically-secure one-way {{w|Hash function|hash function}}, so that even if the password file is stolen, it will be very hard to figure out what the passwords are, so long as the passwords themselves are suitably complex. They also pioneered the use of {{w|Salt (cryptography)|a “salt”}} which makes each password hash completely different even if two users use the same password. See [http://security.blogoverflow.com/2011/07/a-tour-of-password-questions-and-answers/ A tour of password questions and answers] for background on salts and suitably slow hash functions.

Adobe, however, ignored these well-known principles, and instead stored over a hundred million passwords in a reversably encrypted way, using a terrible choice of encryption methods which exposes a great deal of information about the passwords, and does not involve a salt. This password database was recently obtained by someone and released on the Internet.

In particular, Adobe used {{w|Triple DES}}, an older encryption algorithm which can still be relatively secure when properly used but they used it improperly. It works on 64-bit (8 character) blocks. Assuming that the passwords are stored in plain ASCII, this means that a sequence of 8 characters in a password which starts on a character position which is a multiple of eight is always encrypted to the same result. Therefore two passwords starting with “12345678” would start with the same block after being encrypted. Furthermore, this means that you can actually get a very good idea of the length of the password since anything with only one block is a password with length between 1 and 8 characters, and having two blocks implies it has between 9 and 16 characters, etc.

Adobe also stored hints users created for their passwords. That means that an attacker knows not only if the same 8 characters are used for multiple passwords but also has some hints for guessing them. That means that common password portions should be easy to recover and that any user may be “compromised” by someone else using a part of the same password and providing a good hint. As an example, a password having three hints “Big Apple”, “Twin Towers” and “If you can make it there” is probably “New York” (or a simple variation on that). The weakness here is that no decryption and therefore no hard cracking has to take place, you just group the passwords by their encrypted blocks and try to solve them like a crossword puzzle. These weaknesses have already been used to presumably identify a password used by {{w|Edward Snowden}}, as discussed at [http://7habitsofhighlyeffectivehackers.blogspot.com/2013/11/can-someone-be-targeted-using-adobe.html 7 Habits of Highly Effective Hackers: Can someone be targeted using the Adobe breach?].

The examples are not taken from the actual leaked file, since that [http://arstechnica.com/security/2013/11/how-an-epic-blunder-by-adobe-could-strengthen-hand-of-password-crackers/ uses a different format], and the examples are evidently cleverly crafted to make a nice crossword-like puzzle, which can be solved as shown in the Passwords section below.

The title text makes a reference to a previous comic: [[792|Black Hat’s trouble with what to do with stolen passwords]]. It also states that users of pirated Photoshop are the winners here. This is because in order to make Photoshop pirate-able, it was modified (cracked) by removing the requirement for registration so their passwords were not sent to Adobe and therefore are not present in the leaked file.

The title itself is a reference to [http://en.wikipedia.org/wiki/Cryptic_crossword cryptic crosswords]

==Passwords==
Note that characters in the passwords could be upper or lower case, and they may involve common substitutions like "0" (number zero) for "O" (letter O); therefore, the clues cannot guarantee that the answer shown here is precisely correct. Nevertheless, we have plenty of information for a brute force attack.

{|class="wikitable"
! Input
! Hint
! Password
! Explanation
|-
|<tt>4e18acc1ab27a2d6</tt>
|weather vane sword
|<tt>matthias</tt>
|In ''Redwall'', several characters are associated with a sword hung from a weather vane, but only Matthias shares the name of an apostle (6 lines down).
|-
|<tt>4e18acc1ab27a2d6</tt>
|
|<tt>matthias</tt>
|Although no hint was used, we know this password too, since it matches the previous one.
|-
|<tt>4e18acc1ab27a2d6 a0a2876eb1ea1fca</tt>
|name1
|<tt>matthias1</tt>
|Even without knowing the user's name, we already know how this starts, so the clue gives us a pretty good idea how it finishes (and another block useful 2 lines down)
|-
|<tt>8babb6299e06eb6d</tt>
|duh
|<tt>password</tt>
|Unfortunately, this is all too common, and the user practically told us that it's an easy one.
|-
|<tt>8babb6299e06eb6d a0a2876eb1ea1fca</tt>
|
|<tt>password1</tt>
|Although no hint was used, we know this by combining the previous two.
|-
|<tt>8babb6299e06eb6d 85e9da81a8a78adc</tt>
|57
|<tt>password57</tt>
|Since we know how this begins, this is a good guess.
|-
|<tt>4e18acc1ab27a2d6</tt>
|favorite of 12 apostles
|<tt>matthias</tt>
|This has only 12 possibilities to begin with (plus variant spellings, variant lists, and one replacement), but actually we know already which one by combining with the clue 6 lines up.
|-
|<tt>1ab29ae86da6e5ca 7a2d6a0a2876eb1e</tt>
|with your own hand you have done all this
|<tt>Judith1510</tt>
|This is a quotation from Judith 15:10.
|-
|<tt>a1f9b2b6299e7a2b eadec1e6ab797397</tt>
|sexy earlobes
|<tt>Charlie Sheen</tt>
|This refers to an episode of ''Two and a Half Men''. Other answers are possible, but only this one fits the next line.
|-
|<tt>a1f9b2b6299e7a2b 617ab0277727ad85</tt>
|best TOS episode
|<tt>Charlie X</tt>
|"TOS" refers to the original series of ''Star Trek''. Although this had dozens of episodes, only one fits the previous line as well as the next line.
|-
|<tt>39738b7adb0b8af7 617ab0277727ad85</tt>
|Sugarland
|<tt>HoustonTX</tt>
|Sugarland is a suburb of Houston, Texas. This fits with the previous line.
|-
|<tt>1ab29ae86da6e5ca</tt>
|name + jersey#
|<tt>Judith15</tt>
|Even if we knew this user's name, we wouldn't know their jersey number. But the clue 4 lines up already gave us the answer.
|-
|<tt>877ab7889d3862b1</tt>
|alpha
|<tt>abc</tt>
|This password is also far too common, but this clue still isn't enough to narrow it down. Combine with the clue 3 lines below, however, and it's quite easy.
|-
|<tt>877ab7889d3862b1</tt>
|
|<tt>abc</tt>
|No hint, but the same as the surrounding passwords.
|-
|<tt>877ab7889d3862b1</tt>
|
|<tt>abc</tt>
|No hint, but the same as the surrounding passwords.
|-
|<tt>877ab7889d3862b1</tt>
|obvious
|<tt>abc</tt>
|Same as the surrounding passwords.
|-
|<tt>877ab7889d3862b1</tt>
|Michael Jackson
|<tt>abc</tt>
|Michael Jackson did many songs, but only one was alphabetical (3 lines up).
|-
|<tt>38a7c9279cadeb44 9dca1d79d4dec6d5</tt>
|
|
|No hint, but the same as the one below.
|-
|<tt>38a7c9279cadeb44 9dca1d79d4dec6d5</tt>
|HE DID THE MASH, HE DID THE
|<tt></tt>
|probably a reference to the {{w|Monster Mash}}
|
|-
|<tt>38a7c9279cadeb44</tt>
|Purloined
|<tt></tt>
|
|-
|<tt>a8ae5754a2b7af7a 9dca1d79d4dec6d5</tt>
|fav water-3 Pokemon
|<tt></tt>
|''possible second block per [http://bulbapedia.bulbagarden.net/wiki/Water_3_%28Egg_Group%29 Bulbapedia] are "el", "l", "le", "r", "t", "ta", "h", "a"''
|-
|}

==Transcript==
:Hackers recently leaked '''''153 million''''' Adobe user emails, encrypted passwords, and password hints.
:Adobe encrypted the passwords improperly, misusing block-mode 3DES. The result is something wonderful:

<pre>
User password Hint
------------- ----

4e18acc1ab27a2d6 weather vane sword
4e18acc1ab27a2d6
4e18acc1ab27a2d6 a0a2876eb1ea1fca name1
8babb6299e06eb6d duh
8babb6299e06eb6d a0a2876eb1ea1fca
8babb6299e06eb6d 85e9da81a8a78adc 57
4e18acc1ab27a2d6 favorite of 12 apostles
1ab29ae86da6e5ca 7a2d6a0a2876eb1e with your own hand you
have done all this
a1f9b2b6299e7a2b eadec1e6ab797397 sexy earlobes
a1f9b2b6299e7a2b 617ab0277727ad85 best tos episode
39738b7adb0b8af7 617ab0277727ad85 sugarland
1ab29ae86da6e5ca name + jersey#
877ab7889d3862b1 alpha
877ab7889d3862b1
877ab7889d3862b1
877ab7889d3862b1 obvious
877ab7889d3862b1 Michael Jackson
38a7c9279cadeb44 9dca1d79d4dec6d5
38a7c9279cadeb44 9dca1d79d4dec6d5 he did the mash, he did the
38a7c9279cadeb44 Purloined
a8ae5754a2b7af7a 9dca1d79d4dec6d5 fav water-3 pokemon
</pre>

:The greatest crossword puzzle in the history of the world

==Hidden message==
As mentioned on http://filosottile.github.io/analyzing-the-adobe-leaked-passwords/ the data isn't real and contains a hidden message.
Base64 encoded the data blocks (in specific order) read:
<pre>ThiswasnotagooduseofyourtimeButthenagainitwasprobablynotagooduseofmytimeeith
erAndyethereweareXOXOXOLetsLiveHereInThisTinySecretEncodedTextWorldUoreveg==</pre>

{{comic discussion}}

[[Category:Comics with color]]

1286: Encryptic

2013-11-05T13:48:33Z

Qistoph: Correct data block ending in 1fea to a0a2876eb1ea1fca

{{comic
| number = 1286
| date = November 4, 2013
| title = Encryptic
| image = encryptic.png
| titletext = It was bound to happen eventually. This data theft will enable almost limitless [xkcd.com/792]-style password reuse attacks in the coming weeks. There's only one group that comes out of this looking smart: Everyone who pirated Photoshop.
}}

==Explanation==
Web sites and other computers that authenticate users via passwords need to be able to know if the user typed in the right password. But storing the password itself on the computer has been known to be unnecessarily risky since the publication of [http://www.neurosecurity.com/articles/security/passwd.pdf Password Security: A Case History] in 1978. In that paper, Robert Morris and Ken Thompson demonstrated the practice of using a slow, cryptographically-secure one-way {{w|Hash function|hash function}}, so that even if the password file is stolen, it will be very hard to figure out what the passwords are, so long as the passwords themselves are suitably complex. They also pioneered the use of {{w|Salt (cryptography)|a “salt”}} which makes each password hash completely different even if two users use the same password. See [http://security.blogoverflow.com/2011/07/a-tour-of-password-questions-and-answers/ A tour of password questions and answers] for background on salts and suitably slow hash functions.

Adobe, however, ignored these well-known principles, and instead stored over a hundred million passwords in a reversably encrypted way, using a terrible choice of encryption methods which exposes a great deal of information about the passwords, and does not involve a salt. This password database was recently obtained by someone and released on the Internet.

In particular, Adobe used {{w|Triple DES}}, an older encryption algorithm which can still be relatively secure when properly used but they used it improperly. It works on 64-bit (8 character) blocks. Assuming that the passwords are stored in plain ASCII, this means that a sequence of 8 characters in a password which starts on a character position which is a multiple of eight is always encrypted to the same result. Therefore two passwords starting with “12345678” would start with the same block after being encrypted. Furthermore, this means that you can actually get a very good idea of the length of the password since anything with only one block is a password with length between 1 and 8 characters, and having two blocks implies it has between 9 and 16 characters, etc.

Adobe also stored hints users created for their passwords. That means that an attacker knows not only if the same 8 characters are used for multiple passwords but also has some hints for guessing them. That means that common password portions should be easy to recover and that any user may be “compromised” by someone else using a part of the same password and providing a good hint. As an example, a password having three hints “Big Apple”, “Twin Towers” and “If you can make it there” is probably “New York” (or a simple variation on that). The weakness here is that no decryption and therefore no hard cracking has to take place, you just group the passwords by their encrypted blocks and try to solve them like a crossword puzzle. These weaknesses have already been used to presumably identify a password used by {{w|Edward Snowden}}, as discussed at [http://7habitsofhighlyeffectivehackers.blogspot.com/2013/11/can-someone-be-targeted-using-adobe.html 7 Habits of Highly Effective Hackers: Can someone be targeted using the Adobe breach?].

The examples are not taken from the actual leaked file, since that [http://arstechnica.com/security/2013/11/how-an-epic-blunder-by-adobe-could-strengthen-hand-of-password-crackers/ uses a different format], and the examples are evidently cleverly crafted to make a nice crossword-like puzzle, which can be solved as shown in the Passwords section below.

The title text makes a reference to a previous comic: [[792|Black Hat’s trouble with what to do with stolen passwords]]. It also states that users of pirated Photoshop are the winners here. This is because in order to make Photoshop pirate-able, it was modified (cracked) by removing the requirement for registration so their passwords were not sent to Adobe and therefore are not present in the leaked file.

The title itself is a reference to [http://en.wikipedia.org/wiki/Cryptic_crossword cryptic crosswords]

==Passwords==
Note that characters in the passwords could be upper or lower case, and they may involve common substitutions like "0" (number zero) for "O" (letter O); therefore, the clues cannot guarantee that the answer shown here is precisely correct. Nevertheless, we have plenty of information for a brute force attack.

{|class="wikitable"
! Input
! Hint
! Password
! Explanation
|-
|<tt>4e18acc1ab27a2d6</tt>
|weather vane sword
|<tt>matthias</tt>
|In ''Redwall'', several characters are associated with a sword hung from a weather vane, but only Matthias shares the name of an apostle (6 lines down).
|-
|<tt>4e18acc1ab27a2d6</tt>
|
|<tt>matthias</tt>
|Although no hint was used, we know this password too, since it matches the previous one.
|-
|<tt>4e18acc1ab27a2d6 a0a2876eb1ea1fca</tt>
|name1
|<tt>matthias1</tt>
|Even without knowing the user's name, we already know how this starts, so the clue gives us a pretty good idea how it finishes (and another block useful 2 lines down)
|-
|<tt>8babb6299e06eb6d</tt>
|duh
|<tt>password</tt>
|Unfortunately, this is all too common, and the user practically told us that it's an easy one.
|-
|<tt>8babb6299e06eb6d a0a2876eb1ea1fca</tt>
|
|<tt>password1</tt>
|Although no hint was used, we know this by combining the previous two.
|-
|<tt>8babb6299e06eb6d 85e9da81a8a78adc</tt>
|57
|<tt>password57</tt>
|Since we know how this begins, this is a good guess.
|-
|<tt>4e18acc1ab27a2d6</tt>
|favorite of 12 apostles
|<tt>matthias</tt>
|This has only 12 possibilities to begin with (plus variant spellings, variant lists, and one replacement), but actually we know already which one by combining with the clue 6 lines up.
|-
|<tt>1ab29ae86da6e5ca 7a2d6a0a2876eb1e</tt>
|with your own hand you have done all this
|<tt>Judith1510</tt>
|This is a quotation from Judith 15:10.
|-
|<tt>a1f9b2b6299e7a2b eadec1e6ab797397</tt>
|sexy earlobes
|<tt>Charlie Sheen</tt>
|This refers to an episode of ''Two and a Half Men''. Other answers are possible, but only this one fits the next line.
|-
|<tt>a1f9b2b6299e7a2b 617ab0277727ad85</tt>
|best TOS episode
|<tt>Charlie X</tt>
|"TOS" refers to the original series of ''Star Trek''. Although this had dozens of episodes, only one fits the previous line as well as the next line.
|-
|<tt>39738b7adb0b8af7 617ab0277727ad85</tt>
|Sugarland
|<tt>HoustonTX</tt>
|Sugarland is a suburb of Houston, Texas. This fits with the previous line.
|-
|<tt>1ab29ae86da6e5ca</tt>
|name + jersey#
|<tt>Judith15</tt>
|Even if we knew this user's name, we wouldn't know their jersey number. But the clue 4 lines up already gave us the answer.
|-
|<tt>877ab7889d3862b1</tt>
|alpha
|<tt>abc</tt>
|This password is also far too common, but this clue still isn't enough to narrow it down. Combine with the clue 3 lines below, however, and it's quite easy.
|-
|<tt>877ab7889d3862b1</tt>
|
|<tt>abc</tt>
|No hint, but the same as the surrounding passwords.
|-
|<tt>877ab7889d3862b1</tt>
|
|<tt>abc</tt>
|No hint, but the same as the surrounding passwords.
|-
|<tt>877ab7889d3862b1</tt>
|obvious
|<tt>abc</tt>
|Same as the surrounding passwords.
|-
|<tt>877ab7889d3862b1</tt>
|Michael Jackson
|<tt>abc</tt>
|Michael Jackson did many songs, but only one was alphabetical (3 lines up).
|-
|<tt>38a7c9279cadeb44 9dca1d79d4dec6d5</tt>
|
|
|No hint, but the same as the one below.
|-
|<tt>38a7c9279cadeb44 9dca1d79d4dec6d5</tt>
|HE DID THE MASH, HE DID THE
|<tt></tt>
|probably a reference to the {{w|Monster Mash}}
|
|-
|<tt>38a7c9279cadeb44</tt>
|Purloined
|<tt></tt>
|
|-
|<tt>a8ae5754a2b7af7a 9dca1d79d4dec6d5</tt>
|fav water-3 Pokemon
|<tt></tt>
|''possible second block per [http://bulbapedia.bulbagarden.net/wiki/Water_3_%28Egg_Group%29 Bulbapedia] are "el", "l", "le", "r", "t", "ta", "h", "a"''
|-
|}

==Transcript==
:Hackers recently leaked '''''153 million''''' Adobe user emails, encrypted passwords, and password hints.
:Adobe encrypted the passwords improperly, misusing block-mode 3DES. The result is something wonderful:

<pre>
User password Hint
------------- ----

4e18acc1ab27a2d6 weather vane sword
4e18acc1ab27a2d6
4e18acc1ab27a2d6 a0a2876eb1ea1fca name1
8babb6299e06eb6d duh
8babb6299e06eb6d a0a2876eb1ea1fca
8babb6299e06eb6d 85e9da81a8a78adc 57
4e18acc1ab27a2d6 favorite of 12 apostles
1ab29ae86da6e5ca 7a2d6a0a2876eb1e with your own hand you
have done all this
a1f9b2b6299e7a2b eadec1e6ab797397 sexy earlobes
a1f9b2b6299e7a2b 617ab0277727ad85 best tos episode
39738b7adb0b8af7 617ab0277727ad85 sugarland
1ab29ae86da6e5ca name + jersey#
877ab7889d3862b1 alpha
877ab7889d3862b1
877ab7889d3862b1
877ab7889d3862b1 obvious
877ab7889d3862b1 Michael Jackson
38a7c9279cadeb44 9dca1d79d4dec6d5
38a7c9279cadeb44 9dca1d79d4dec6d5 he did the mash, he did the
38a7c9279cadeb44 Purloined
a8ae5754a2b7af7a 9dca1d79d4dec6d5 fav water-3 pokemon
</pre>

:The greatest crossword puzzle in the history of the world

{{comic discussion}}

[[Category:Comics with color]]