S/KEY - Revision history

Henryk: /* Full example */

2004-11-07T03:02:02Z

Full example

← Older revision		Revision as of 03:02, 7 November 2004
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	alice@gleam alice $ <i>skey -t md5 -n 5 98 glea92484</i>		alice@gleam alice $ <i>skey -t md5 -n 5 98 glea92484</i>
	Reminder - Do not use this program while logged in via telnet or rlogin.		Reminder - Do not use this program while logged in via telnet or rlogin.
	Enter secret password:		Enter secret password: <i><s>Soylent green is people.</s></i>
	94: BON JESS KANE AX DEEM GANG		94: BON JESS KANE AX DEEM GANG
	95: FILE DICE INCH ELY RUBE COED		95: FILE DICE INCH ELY RUBE COED

Henryk: /* Full example */

2004-11-07T02:49:23Z

Full example

← Older revision		Revision as of 02:49, 7 November 2004
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	(Note: <i>Italic text</i> is keyboard input, <i><s>Striked italic text</s></i> is hidden keyboard input.)		(Note: <i>Italic text</i> is keyboard input, <i><s>Striked italic text</s></i> is hidden keyboard input.)

	alice@gleam: alice $ <i>skeyinit -t md5</i>		alice@gleam alice $ <i>skeyinit -t md5</i>
	Password: <i><s>unix password</s></i>		Password: <i><s>unix password</s></i>
	[Adding alice]		[Adding alice]
Line 51:		Line 51:
	Next login password: JOEY BUB LIVE URGE MOOD TRUE		Next login password: JOEY BUB LIVE URGE MOOD TRUE

	alice@gleam: alice $ <i>su - -c "grep alice /etc/skey/skeykeys"</i>		alice@gleam alice $ <i>su - -c "grep alice /etc/skey/skeykeys"</i>
	Password: <i><s>unix password</s></i>		Password: <i><s>unix password</s></i>
	alice md5 0099 glea92484 a2611ac2f92be7e0 Nov 07,2004 02:54:52		alice md5 0099 glea92484 a2611ac2f92be7e0 Nov 07,2004 02:54:52

	alice@gleam: alice $ <i>skey -t md5 -n 5 98 glea92484</i>		alice@gleam alice $ <i>skey -t md5 -n 5 98 glea92484</i>
	Reminder - Do not use this program while logged in via telnet or rlogin.		Reminder - Do not use this program while logged in via telnet or rlogin.
	Enter secret password:		Enter secret password:
Line 64:		Line 64:
	98: DAY LEFT BOON MAUL NO WINE		98: DAY LEFT BOON MAUL NO WINE

	alice@gleam: alice $ <i>ssh localhost</i>		alice@gleam alice $ <i>ssh localhost</i>
	challenge s/key 98 glea92484		challenge s/key 98 glea92484
	password: <i><s>DAY LEFT BOON MAUL NO WINE</s></i>		password: <i><s>DAY LEFT BOON MAUL NO WINE</s></i>
	Last login: Sun Nov 7 02:51:40 2004 from localhost		Last login: Sun Nov 7 02:51:40 2004 from localhost

	alice@gleam: alice $ <i>logout</i>		alice@gleam alice $ <i>logout</i>
	Connection to localhost closed.		Connection to localhost closed.

	alice@gleam: alice $ <i>ssh localhost</i>		alice@gleam alice $ <i>ssh localhost</i>
	challenge s/key 97 glea92484		challenge s/key 97 glea92484
	password: <i><s>FIR FOOT BALL GIN RAN LOOK</s></i>		password: <i><s>FIR FOOT BALL GIN RAN LOOK</s></i>
	Last login: Sun Nov 7 02:55:50 2004 from localhost		Last login: Sun Nov 7 02:55:50 2004 from localhost

	alice@gleam: alice $ <i>logout</i>		alice@gleam alice $ <i>logout</i>
	Connection to localhost closed.		Connection to localhost closed.

	alice@gleam: alice $ <i>su - -c "grep alice /etc/skey/skeykeys"</i>		alice@gleam alice $ <i>su - -c "grep alice /etc/skey/skeykeys"</i>
	Password: <i><s>unix password</s></i>		Password: <i><s>unix password</s></i>
	alice md5 0097 glea92484 141095470b936564 Nov 07,2004 02:56:05		alice md5 0097 glea92484 141095470b936564 Nov 07,2004 02:56:05

			In the example the user alice first initializes the S/KEY system. To be able to do this she must authenticate with her regular unix password and is then asked for her new, secret passphrase. When the process completes successfully a new entry is created in the skeykeys file giving the hash algorithm, the initial sequence number, the seed (which was created from the hostname and some number) the actual hash in hex and a timestamp. Alice then uses the <code>skey</code> utitlity to print the next authentication password(s) in Six Word Format and logs in to the machine using these passwords. Obviously at each login attempt a different password is needed. After each successful login the skeykeys file is modified to reflect the last hash (in hex) and the corresponding sequence number.

Henryk: /* Full example */

2004-11-07T02:36:34Z

Full example

← Older revision		Revision as of 02:36, 7 November 2004
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	Following is a full example of the complete process. The user's name is <var>alice</var>. The host system is a Gentoo Linux box with an S/KEY [[PAM]] module. The passphrase will be <code>Soylent green is people.</code>.		Following is a full example of the complete process. The user's name is <var>alice</var>. The host system is a Gentoo Linux box with an S/KEY [[PAM]] module. The passphrase will be <code>Soylent green is people.</code>.

	(Note: ''Italic text'' ~~are~~ keyboard ~~inputs~~, ~~'''Bold~~ text~~'''~~ ~~are~~ hidden keyboard ~~inputs~~.)		(Note: <i>Italic text</i> is keyboard input, <i><s>Striked italic text</s></i> is hidden keyboard input.)

	alice@gleam: alice $ ''skeyinit -t md5''		alice@gleam: alice $ <i>skeyinit -t md5</i>
	Password: ~~'''~~unix password~~'''~~		Password: <i><s>unix password</s></i>
	[Adding alice]		[Adding alice]
	Reminder - Only use this method if you are directly connected		Reminder - Only use this method if you are directly connected
Line 45:		Line 45:
	or rlogin, exit with no password and use skeyinit -s.		or rlogin, exit with no password and use skeyinit -s.

	Enter secret password: ~~'''~~Soylent green is people.~~'''~~		Enter secret password: <i><s>Soylent green is people.</s></i>
	Again secret password: ~~'''~~Soylent green is people.~~'''~~		Again secret password: <i><s>Soylent green is people.</s></i>

	ID alice skey is otp-md5 99 glea92484		ID alice skey is otp-md5 99 glea92484
	Next login password: JOEY BUB LIVE URGE MOOD TRUE		Next login password: JOEY BUB LIVE URGE MOOD TRUE

	alice@gleam: alice $ ''su - -c "grep alice /etc/skey/skeykeys"''		alice@gleam: alice $ <i>su - -c "grep alice /etc/skey/skeykeys"</i>
	Password: ~~'''~~unix password~~'''~~		Password: <i><s>unix password</s></i>
	alice md5 0099 glea92484 a2611ac2f92be7e0 Nov 07,2004 02:54:52		alice md5 0099 glea92484 a2611ac2f92be7e0 Nov 07,2004 02:54:52

	alice@gleam: alice $ ''skey -t md5 -n 5 98 glea92484''		alice@gleam: alice $ <i>skey -t md5 -n 5 98 glea92484</i>
	Reminder - Do not use this program while logged in via telnet or rlogin.		Reminder - Do not use this program while logged in via telnet or rlogin.
	Enter secret password:		Enter secret password:
Line 64:		Line 64:
	98: DAY LEFT BOON MAUL NO WINE		98: DAY LEFT BOON MAUL NO WINE

	alice@gleam: alice $ ''ssh localhost''		alice@gleam: alice $ <i>ssh localhost</i>
	challenge s/key 98 glea92484		challenge s/key 98 glea92484
	password: ~~'''~~DAY LEFT BOON MAUL NO WINE~~'''~~		password: <i><s>DAY LEFT BOON MAUL NO WINE</s></i>
	Last login: Sun Nov 7 02:51:40 2004 from localhost		Last login: Sun Nov 7 02:51:40 2004 from localhost

	alice@gleam: alice $ ''logout''		alice@gleam: alice $ <i>logout</i>
	Connection to localhost closed.		Connection to localhost closed.

	alice@gleam: alice $ ''ssh localhost''		alice@gleam: alice $ <i>ssh localhost</i>
	challenge s/key 97 glea92484		challenge s/key 97 glea92484
	password: ~~'''~~FIR FOOT BALL GIN RAN LOOK~~'''~~		password: <i><s>FIR FOOT BALL GIN RAN LOOK</s></i>
	Last login: Sun Nov 7 02:55:50 2004 from localhost		Last login: Sun Nov 7 02:55:50 2004 from localhost

	alice@gleam: alice $ ''logout''		alice@gleam: alice $ <i>logout</i>
	Connection to localhost closed.		Connection to localhost closed.

	alice@gleam: alice $ ''su - -c "grep alice /etc/skey/skeykeys"''		alice@gleam: alice $ <i>su - -c "grep alice /etc/skey/skeykeys"</i>
	Password: ~~'''~~unix password~~'''~~		Password: <i><s>unix password</s></i>
	alice md5 0097 glea92484 141095470b936564 Nov 07,2004 02:56:05		alice md5 0097 glea92484 141095470b936564 Nov 07,2004 02:56:05

Henryk: /* Full example */

2004-11-07T02:27:07Z

Full example

← Older revision		Revision as of 02:27, 7 November 2004
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	alice@gleam: alice $ ''skeyinit -t md5''		alice@gleam: alice $ ''skeyinit -t md5''
	Password: '''unix password'''		Password: '''unix password'''
	~~<code>~~[Adding alice]~~<br>~~		[Adding alice]
	Reminder - Only use this method if you are directly connected~~<br>~~		Reminder - Only use this method if you are directly connected
	or have an encrypted channel. If you are using telnet~~<br>~~		or have an encrypted channel. If you are using telnet
	or rlogin, exit with no password and use skeyinit -s.~~<br>~~		or rlogin, exit with no password and use skeyinit -s.

	<br>
	Enter secret password: '''Soylent green is people.'''~~<br>~~		Enter secret password: '''Soylent green is people.'''
	Again secret password: '''Soylent green is people.'''~~<br>~~		Again secret password: '''Soylent green is people.'''

	<br>
	ID alice skey is otp-md5 99 glea92484~~<br>~~		ID alice skey is otp-md5 99 glea92484
	Next login password: JOEY BUB LIVE URGE MOOD TRUE~~<br>~~		Next login password: JOEY BUB LIVE URGE MOOD TRUE

	<br>
	alice@gleam: alice $ ''su - -c "grep alice /etc/skey/skeykeys"''~~<br>~~		alice@gleam: alice $ ''su - -c "grep alice /etc/skey/skeykeys"''
	Password: '''unix password'''~~<br>~~		Password: '''unix password'''
	alice md5 0099 glea92484 a2611ac2f92be7e0 Nov 07,2004 02:54:52~~<br>~~		alice md5 0099 glea92484 a2611ac2f92be7e0 Nov 07,2004 02:54:52

	alice@gleam: alice $ ''skey -t md5 -n 5 98 glea92484''~~<br>~~		alice@gleam: alice $ ''skey -t md5 -n 5 98 glea92484''
	Reminder - Do not use this program while logged in via telnet or rlogin.~~<br>~~		Reminder - Do not use this program while logged in via telnet or rlogin.
	Enter secret password: ~~<br>~~		Enter secret password:
	94: BON JESS KANE AX DEEM GANG ~~<br>~~		94: BON JESS KANE AX DEEM GANG
	95: FILE DICE INCH ELY RUBE COED ~~<br>~~		95: FILE DICE INCH ELY RUBE COED
	96: KLAN COOL JADE DIRT RENA SEE ~~<br>~~		96: KLAN COOL JADE DIRT RENA SEE
⚫	97: FIR FOOT BALL GIN RAN LOOK ~~<br>~~
	98: ~~DAY~~ ~~LEFT~~ ~~BOON~~ ~~MAUL~~ NO ~~WINE~~ ~~<br>~~		97: FIR FOOT BALL GIN RAN LOOK
		⚫	98: DAY LEFT BOON MAUL NO WINE
⚫	alice@gleam: alice $ ''ssh localhost''~~<br>~~

⚫	challenge s/key 98 glea92484~~<br>~~
		⚫	alice@gleam: alice $ ''ssh localhost''
⚫	~~password~~: ~~'''~~DAY LEFT BOON MAUL NO WINE~~'''<br>~~
		⚫	challenge s/key 98 glea92484
⚫	Last login: Sun Nov 7 02:51:40 2004 from localhost~~<br>~~
		⚫	password: '''DAY LEFT BOON MAUL NO WINE'''
	alice@gleam: alice $ ''logout''<br>
		⚫	Last login: Sun Nov 7 02:51:40 2004 from localhost
⚫	Connection to localhost closed.~~<br>~~

	<br>
	alice@gleam: alice $ ''~~ssh localhost~~''~~<br>~~		alice@gleam: alice $ ''logout''
		⚫	Connection to localhost closed.
⚫	challenge s/key 97 glea92484~~<br>~~

⚫	password: '''~~FIR~~ ~~FOOT~~ ~~BALL~~ ~~GIN~~ ~~RAN~~ ~~LOOK~~'''~~<br>~~
	~~Last login~~: ~~Sun Nov 7 02:55:50~~ ~~2004~~ ~~from~~ localhost~~<br>~~		alice@gleam: alice $ ''ssh localhost''
		⚫	challenge s/key 97 glea92484
	<br>
		⚫	password: '''FIR FOOT BALL GIN RAN LOOK'''
	alice@gleam: alice $ ''logout''<br>
			Last login: Sun Nov 7 02:55:50 2004 from localhost
⚫	Connection to localhost closed.~~<br>~~

	<br>
	alice@gleam: alice $ ''~~su - -c "grep alice /etc/skey/skeykeys"~~''~~<br>~~		alice@gleam: alice $ ''logout''
		⚫	Connection to localhost closed.
⚫	Password: '''unix password'''~~<br>~~

⚫	alice md5 0097 glea92484 141095470b936564 Nov 07,2004 02:56:05~~<br>~~
			alice@gleam: alice $ ''su - -c "grep alice /etc/skey/skeykeys"''
	</code>
		⚫	Password: '''unix password'''
		⚫	alice md5 0097 glea92484 141095470b936564 Nov 07,2004 02:56:05

Henryk: /* Full example */

2004-11-07T02:17:58Z

Full example

← Older revision		Revision as of 02:17, 7 November 2004
Line 38:		Line 38:
	(Note: ''Italic text'' are keyboard inputs, '''Bold text''' are hidden keyboard inputs.)		(Note: ''Italic text'' are keyboard inputs, '''Bold text''' are hidden keyboard inputs.)

	~~<code>~~alice@gleam: alice $ ''skeyinit -t md5''~~<br>~~		alice@gleam: alice $ ''skeyinit -t md5''
	Password: '''unix password'''~~<br>~~		Password: '''unix password'''
	[Adding alice]<br>		<code>[Adding alice]<br>
	Reminder - Only use this method if you are directly connected<br>		Reminder - Only use this method if you are directly connected<br>
	or have an encrypted channel. If you are using telnet<br>		or have an encrypted channel. If you are using telnet<br>

Henryk: /* Full example */

2004-11-07T02:10:22Z

Full example

← Older revision		Revision as of 02:10, 7 November 2004
Line 35:		Line 35:

	Following is a full example of the complete process. The user's name is <var>alice</var>. The host system is a Gentoo Linux box with an S/KEY [[PAM]] module. The passphrase will be <code>Soylent green is people.</code>.		Following is a full example of the complete process. The user's name is <var>alice</var>. The host system is a Gentoo Linux box with an S/KEY [[PAM]] module. The passphrase will be <code>Soylent green is people.</code>.

			(Note: ''Italic text'' are keyboard inputs, '''Bold text''' are hidden keyboard inputs.)

			<code>alice@gleam: alice $ ''skeyinit -t md5''<br>
			Password: '''unix password'''<br>
			[Adding alice]<br>
			Reminder - Only use this method if you are directly connected<br>
			or have an encrypted channel. If you are using telnet<br>
			or rlogin, exit with no password and use skeyinit -s.<br>
			<br>
			Enter secret password: '''Soylent green is people.'''<br>
			Again secret password: '''Soylent green is people.'''<br>
			<br>
			ID alice skey is otp-md5 99 glea92484<br>
			Next login password: JOEY BUB LIVE URGE MOOD TRUE<br>
			<br>
			alice@gleam: alice $ ''su - -c "grep alice /etc/skey/skeykeys"''<br>
			Password: '''unix password'''<br>
			alice md5 0099 glea92484 a2611ac2f92be7e0 Nov 07,2004 02:54:52<br>
			alice@gleam: alice $ ''skey -t md5 -n 5 98 glea92484''<br>
			Reminder - Do not use this program while logged in via telnet or rlogin.<br>
			Enter secret password: <br>
			94: BON JESS KANE AX DEEM GANG <br>
			95: FILE DICE INCH ELY RUBE COED <br>
			96: KLAN COOL JADE DIRT RENA SEE <br>
			97: FIR FOOT BALL GIN RAN LOOK <br>
			98: DAY LEFT BOON MAUL NO WINE <br>
			alice@gleam: alice $ ''ssh localhost''<br>
			challenge s/key 98 glea92484<br>
			password: '''DAY LEFT BOON MAUL NO WINE'''<br>
			Last login: Sun Nov 7 02:51:40 2004 from localhost<br>
			alice@gleam: alice $ ''logout''<br>
			Connection to localhost closed.<br>
			<br>
			alice@gleam: alice $ ''ssh localhost''<br>
			challenge s/key 97 glea92484<br>
			password: '''FIR FOOT BALL GIN RAN LOOK'''<br>
			Last login: Sun Nov 7 02:55:50 2004 from localhost<br>
			<br>
			alice@gleam: alice $ ''logout''<br>
			Connection to localhost closed.<br>
			<br>
			alice@gleam: alice $ ''su - -c "grep alice /etc/skey/skeykeys"''<br>
			Password: '''unix password'''<br>
			alice md5 0097 glea92484 141095470b936564 Nov 07,2004 02:56:05<br>
			</code>

Henryk at 01:31, 7 November 2004

2004-11-07T01:31:33Z

← Older revision		Revision as of 01:31, 7 November 2004
Line 31:		Line 31:

	Then, when doing authentication, the user can mostly ignore the challenge and simply take the next password from her list, marking all used passwords in some way.		Then, when doing authentication, the user can mostly ignore the challenge and simply take the next password from her list, marking all used passwords in some way.

			== Full example ==

			Following is a full example of the complete process. The user's name is <var>alice</var>. The host system is a Gentoo Linux box with an S/KEY [[PAM]] module. The passphrase will be <code>Soylent green is people.</code>.

Henryk: /* Authentication */

2004-11-07T01:26:24Z

Authentication

← Older revision		Revision as of 01:26, 7 November 2004
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	== Authentication ==		== Authentication ==

	When authentication is desired the host transmits a challenge to the user ~~which consists~~ of the <math>seed</math> and <math>n-1</math> (where <math>h_n</math> is the hash value that is stored on the host) and also ~~mentions~~ the <math>H_o</math> to be used. The user then comes up with <math>h_{n-1}</math> and transmits this hash to the host. The host computes <math>H(h_{n-1}, seed)</math> and compares this value with the one in its storage. The user is authenticated, if the result matches in which case <math>h_{n-1}</math> and <math>n-1</math> are stored on the host (replacing <math>h_n</math> and <math>n</math>). Otherwise the authentication fails.		When authentication is desired the host transmits a challenge to the user consisting of the <math>seed</math> and <math>n-1</math> (where <math>h_n</math> is the hash value that is stored on the host) and also naming the <math>H_o</math> to be used. The user then comes up with <math>h_{n-1}</math> and transmits this hash to the host. The host computes <math>H(h_{n-1}, seed)</math> and compares this value with the one in its storage. The user is authenticated, if the result matches in which case <math>h_{n-1}</math> and <math>n-1</math> are stored on the host (replacing <math>h_n</math> and <math>n</math>). Otherwise the authentication fails.

			The system is secure against an eavesdropping attacker because the next authentic hash (<math>h_{n-1}</math>) can not be easily computed from a transmitted hash (<math>h_{n}</math>). For the very same reason it also is secure against read-only attacks on the host's password storage where only <math>h_{n}</math> is stored.

			The user has several ways to come up with <math>h_{n-1}</math>. The most obvious approach would be a locally run program on the computer the user wants to authenticate from. This program would take the user's passphrase, the seed and the hash algorithm and compute the necessary authentication hash. As the challenge is transmitted in a machine-parseable format the latter two values can be determined automatically and a modified telnet client could make the process completely transparent to the user, simply prompting her for her passphrase. A similar approach would be to use a pocket calculator style device to user could carry with her.

			The most interesting feature with regard to usage as One-Time Password system however is the fact that all the challenges are known in advance and thus the authentication hashes can be computed in advance. Thus the user can use a program on a trusted host, enter the seed and initial sequence number from the initialization process and generate a list of all (or the next 23 or so) authentication hashes. She can then print this list and take it with her.

			Then, when doing authentication, the user can mostly ignore the challenge and simply take the next password from her list, marking all used passwords in some way.

Henryk at 01:12, 7 November 2004

2004-11-07T01:12:09Z

← Older revision		Revision as of 01:12, 7 November 2004
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	This value is stored together with the seed and the sequence number somewhere on the host that is to be authenticated to. As the passphrase must not be exposed to any attacker, the calculation should be done on a trustworthy system over a secure connection. The <math>h_I</math> however does not need to be kept secret.		This value is stored together with the seed and the sequence number somewhere on the host that is to be authenticated to. As the passphrase must not be exposed to any attacker, the calculation should be done on a trustworthy system over a secure connection. The <math>h_I</math> however does not need to be kept secret.

			== Authentication ==

			When authentication is desired the host transmits a challenge to the user which consists of the <math>seed</math> and <math>n-1</math> (where <math>h_n</math> is the hash value that is stored on the host) and also mentions the <math>H_o</math> to be used. The user then comes up with <math>h_{n-1}</math> and transmits this hash to the host. The host computes <math>H(h_{n-1}, seed)</math> and compares this value with the one in its storage. The user is authenticated, if the result matches in which case <math>h_{n-1}</math> and <math>n-1</math> are stored on the host (replacing <math>h_n</math> and <math>n</math>). Otherwise the authentication fails.

Henryk: /* Initialization */

2004-11-07T01:03:08Z

Initialization

← Older revision		Revision as of 01:03, 7 November 2004
Line 8:		Line 8:

	== Initialization ==		== Initialization ==
			The system must be initialized before it can be used. During this process a <math>seed</math> (also called system identifier) is generated which can be between 1 and 16 characters in length and may for example be made up of the host name's first few characters and some random numbers. The seed should be different for each system the same passphrase is used on and should not be reused during successive initializations (at least as long the passphrase is not changed).
	Before a user can use the system it must be initialized.

			During the initialization step the user must choose a password or passphrase (<math>pass</math>) which should be at least 10 characters long and must be kept secret. Reusing the same passphrase on different systems should be safe, as long as the seeds differ from each other.

			A further parameter choosed during initialization is the initial sequence number or iteration count. A good choice would for example be 100. This number is decremented at each authentication process, and the system must be reinitialized once the sequence number reaches zero.

			When initializing the system, a value <math>h_I</math> is computed, where <math>I</math> is the initial sequence number. The computation is done through:<br>
			<math>h_0 := H(pass, seed)</math><br>
			<math>h_{n+1} := H(h_n, seed)</math>

			This value is stored together with the seed and the sequence number somewhere on the host that is to be authenticated to. As the passphrase must not be exposed to any attacker, the calculation should be done on a trustworthy system over a secure connection. The <math>h_I</math> however does not need to be kept secret.