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The S/KEY One-Time Password System (RFC1760)

IP.com Disclosure Number: IPCOM000004011D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 9 page(s) / 29K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

N. Haller: AUTHOR

Abstract

This document describes the S/KEY* One-Time Password system as released for public use by Bellcore and as described in reference [3]. A reference implementation and documentation are available by anonymous ftp from ftp.bellcore.com in the directories pub/nmh/...

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 9% of the total text.

Network Working Group N. Haller

Request for Comments: 1760 Bellcore

Category: Informational February 1995

The S/KEY One-Time Password System

Status of this Memo

This memo provides information for the Internet community. This memo

does not specify an Internet standard of any kind. Distribution of

this memo is unlimited.

Abstract

This document describes the S/KEY* One-Time Password system as

released for public use by Bellcore and as described in reference

[3]. A reference implementation and documentation are available by

anonymous ftp from ftp.bellcore.com in the directories pub/nmh/...

Overview

One form of attack on computing system connected to the Internet is

eavesdropping on network connections to obtain login id's and

passwords of legitimate users. The captured login id and password

are, at a later time, used gain access to the system. The S/KEY

One-Time Password system is designed to counter this type of attack,

called a replay attack.

With the S/KEY system, only a single use password ever crosses the

network. The user's secret pass-phrase never crosses the network at

any time, including during login or when executing other commands

requiring authentication such as the UNIX commands passwd or su.

Thus, it is not vulnerable to eavesdropping/replay attacks. Added

security is provided by the property that no secret information need

be stored on any system, including the host being protected.

The S/KEY system protects against external passive attacks against

the authentication subsystem. It does not prevent a network

eavesdropper from gaining access to private information, and does not

provide protection against "inside jobs" or against active attacks

where the potential intruder as able to intercept and modify the

packet stream.

Introduction

There are two sides to the operation of the S/KEY one-time password

system. On the client side, the appropriate one-time password must

be generated. On the host side, the server must verify the one-time

password and permit the secure changing of the user's secret pass-

phrase.

An S/KEY system client passes the user's secret pass-phrase through

multiple applications of a secure hash function to produce a one-time

password. On each use, the number of applications is reduced by one.

Thus a unique sequence of passwords is generated. The S/KEY system

host verifies the one-time password by making one pass though the

secure hash function and comparing the result wit...