1.\" opie.4: Overview of the OPIE software.
2.\"
3.\" %%% portions-copyright-cmetz-96
4.\" Portions of this software are Copyright 1996-1998 by Craig Metz, All Rights
5.\" Reserved. The Inner Net License Version 2 applies to these portions of
6.\" the software.
7.\" You should have received a copy of the license with this software. If
8.\" you didn't get a copy, you may request one from <license@inner.net>.
9.\"
10.\" Portions of this software are Copyright 1995 by Randall Atkinson and Dan
11.\" McDonald, All Rights Reserved. All Rights under this copyright are assigned
12.\" to the U.S. Naval Research Laboratory (NRL). The NRL Copyright Notice and
13.\" License Agreement applies to this software.
14.\"
15.\" History:
16.\"
17.\" Modified by cmetz for OPIE 2.2. Removed MJR DES documentation. Removed
18.\" references to the old square brackets challenge delimiters.
19.\" Modified at NRL for OPIE 2.01. Updated UNIX trademark credit.
20.\" Definition of "seed" written by Neil Haller of Bellcore
21.\" Written at NRL for OPIE 2.0.
22.\"
23.\" $FreeBSD: head/contrib/opie/opie.4 59121 2000-04-10 11:18:54Z kris $
24.\"
25.TH OPIE 4 "January 10, 1995"
26.SH NAME
27.B OPIE \- One-time Passwords In Everything
28.SH DESCRIPTION
29.LP
30OPIE is a package derived from the Bellcore S/Key Version 1 distribution
31that helps to secure a system against replay attacks (see below). It does so
--- 50 unchanged lines hidden (view full) ---
82.I response
83A packet of information generated from a challenge that is used by a system to
84authenticate a user. In OPIE, this is a group of six words that is generated by
85the calculator given the challenge and the secret password. For example,
86"PUP SOFT ROSE BIAS FLAG END".
87.TP
88.I seed
89A piece of information that is used in conjunction with the secret password
90and sequence numer to compute the response. Its purpose is to allow the same
91secret password to be used for multiple sequences, by changing the seed, or
92for authentication to multiple machines by using different seeds.
93.TP
94.I sequence number
95A counter used to keep track of key iterations. In OPIE, each time a successful
96response is received by the system, the sequence number is decremented. For
97example, "95".
98.TP
--- 39 unchanged lines hidden (view full) ---
138
139.SH THE S/KEY ALGORITHM
140
141A solution to this whole problem was invented by Lamport in 1981. This
142technique was implemented by Haller, Karn, and Walden at Bellcore. They
143created a free software package called "S/Key" that used an algorithm
144called a cryptographic checksum. A cryptographic checksum is a strong one-way
145function such that, knowing the result of such a function, an attacker still
146cannot feasably determine the input. Further, unlike cyclic redundancy
147checksums (CRCs), cryptographic checksums have few inputs that result in the
148same output.
149.LP
150In S/Key, what changes is the number of
151times the password is run through the secure hash. The password is run through
152the secure hash once, then the output of the hash is run through the secure
153hash again, that output is run through the secure hash again, and so on until
154the number of times the password has been run through the secure hash is equal
--- 185 unchanged lines hidden ---
2.\"
3.\" %%% portions-copyright-cmetz-96
4.\" Portions of this software are Copyright 1996-1998 by Craig Metz, All Rights
5.\" Reserved. The Inner Net License Version 2 applies to these portions of
6.\" the software.
7.\" You should have received a copy of the license with this software. If
8.\" you didn't get a copy, you may request one from <license@inner.net>.
9.\"
10.\" Portions of this software are Copyright 1995 by Randall Atkinson and Dan
11.\" McDonald, All Rights Reserved. All Rights under this copyright are assigned
12.\" to the U.S. Naval Research Laboratory (NRL). The NRL Copyright Notice and
13.\" License Agreement applies to this software.
14.\"
15.\" History:
16.\"
17.\" Modified by cmetz for OPIE 2.2. Removed MJR DES documentation. Removed
18.\" references to the old square brackets challenge delimiters.
19.\" Modified at NRL for OPIE 2.01. Updated UNIX trademark credit.
20.\" Definition of "seed" written by Neil Haller of Bellcore
21.\" Written at NRL for OPIE 2.0.
22.\"
23.\" $FreeBSD: head/contrib/opie/opie.4 59121 2000-04-10 11:18:54Z kris $
24.\"
25.TH OPIE 4 "January 10, 1995"
26.SH NAME
27.B OPIE \- One-time Passwords In Everything
28.SH DESCRIPTION
29.LP
30OPIE is a package derived from the Bellcore S/Key Version 1 distribution
31that helps to secure a system against replay attacks (see below). It does so
--- 50 unchanged lines hidden (view full) ---
82.I response
83A packet of information generated from a challenge that is used by a system to
84authenticate a user. In OPIE, this is a group of six words that is generated by
85the calculator given the challenge and the secret password. For example,
86"PUP SOFT ROSE BIAS FLAG END".
87.TP
88.I seed
89A piece of information that is used in conjunction with the secret password
90and sequence numer to compute the response. Its purpose is to allow the same
91secret password to be used for multiple sequences, by changing the seed, or
92for authentication to multiple machines by using different seeds.
93.TP
94.I sequence number
95A counter used to keep track of key iterations. In OPIE, each time a successful
96response is received by the system, the sequence number is decremented. For
97example, "95".
98.TP
--- 39 unchanged lines hidden (view full) ---
138
139.SH THE S/KEY ALGORITHM
140
141A solution to this whole problem was invented by Lamport in 1981. This
142technique was implemented by Haller, Karn, and Walden at Bellcore. They
143created a free software package called "S/Key" that used an algorithm
144called a cryptographic checksum. A cryptographic checksum is a strong one-way
145function such that, knowing the result of such a function, an attacker still
146cannot feasably determine the input. Further, unlike cyclic redundancy
147checksums (CRCs), cryptographic checksums have few inputs that result in the
148same output.
149.LP
150In S/Key, what changes is the number of
151times the password is run through the secure hash. The password is run through
152the secure hash once, then the output of the hash is run through the secure
153hash again, that output is run through the secure hash again, and so on until
154the number of times the password has been run through the secure hash is equal
--- 185 unchanged lines hidden ---