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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and apparatus for providing remote
user authentication in a public network. More particularly, the present
invention provides methods and apparatus for remote authentication using a
one-time password scheme having a secure out-of-band channel for initial
password delivery.
2. Art Background
Over the past few years, the networking of computers for electronic mail
("e-mail") communication and dam transfer has grown from simple local area
networks to a global network referred to as the "Internet". The Internet
comprises a spiderweb of networks which criss-cross the globe and permit
users to send and receive e-mail messages, transfer data and access remote
data bases between computers coupled to servers. In addition to fixed
positions on the Internet, computer systems, such as for example, lap top
computers, may be physically moved from one location on the network to
another. Wireless links coupling the computers to the Internet, such as
direct satellite links, also permit users to access the Internet from
remote areas.
As the number of users on the Internet has grown, so have concerns
regarding network security. Many businesses and government organizations
utilize the Internet for the transfer of business information, government
project data and other information which may be considered confidential.
Due to the size and complexity of the Internet, the opportunity for an
intruder to intercept messages and gain access to confidential information
has become a significant concern. The Internet community has established
message encryption and authentication procedures for Internet electronic
mail. These encryption and authentication procedures are known as privacy
enhanced mail (PEM). The PEM protocol establishes procedures to provide
for enhanced privacy in e-mail services over the Internet. The PEM
protocol is intended to be compatible with a wide range of key management
approaches including symmetric (secret key) and asymmetric (public key)
approaches for the encryption of data encrypting keys. Privacy enhanced
mail services assure message integrity, and are offered through the use of
end-to-end cryptography between originator and recipient processes at or
above the user level. No special processing requirements are imposed on
the message transfer system at endpoints, or at intermediate relay sites
on the Internet. The reader is referred to the PEM RFC documents and
incorporated herein by reference, entitled: "Privacy Enhancement for
Internet Electronic Mail", Parts I-IV, RFCS 1421-1424, available on the
Internet at home/internet/rfcs on files rfc1421-rfc1424 (hereinafter at
times referred to as "PEM Protocols").
However, although privacy enhanced mail service is available on the
Internet, all current applications on the Internet (commonly referred to
as "legacy" applications), such as Telnet, File Transfer Protocol ("ftp"),
and the like, use simple authentication having reusable passwords.
Although it is generally understood that strong authentication using
crypto-techniques would provide enhanced password security on the
Internet, retrofitting the existing installed base of network applications
with such a strong authentication mechanism would take some period of
time. In the interim, an intruder can monitor the network and intercept
passwords transmitted over the Internet. Since all passwords are currently
transmitted from user to a remote server in unencrypted ("clear") form,
Internet users are vulnerable to an intruder determining their password,
and later logging on to a server utilizing the stolen password of a
legitimate user. In fact, there have been cases where intruders have
tapped the Internet at well known public sites and have accumulated
literally thousands of legitimate valid passwords. Thus, the Internet must
be viewed as a large insecure channel in which passwords are transmitted
in the clear, and may be acquired by unauthorized parties.
As will be described, the present invention provides methods and apparatus
to permit an Internet user to acquire a password which is good for only a
one time use. Through the use of the existing privacy enhanced mail system
on the Internet, the present invention ensures that only the legitimate
user can gain access to the password. Moreover, as will be described, the
present invention does not require the retrofitting of existing
applications and computers with a strong authentication mechanism.
SUMMARY OF THE INVENTION
The present invention provides an improved method and apparatus for user
authentication in a network environment between a client computer
("workstation") and a remote destination server coupled to a network. A
user operating the client workstation provides a login address as an
anonymous ftp (file transfer protocol) request, and a password as the
user's e-mail address. The destination server compares the user's e-mail
address provided as a password to a list of authorized users' addresses.
If the user e-mail address provided is not on the destination server's
list of authorized user addresses, then the user login request is
automatically denied. If the user's e-mall address is located on the list
of authorized users' addresses maintained by the destination server, the
destination server generates a random number (X), and encrypts the random
number in an ASCII representation using encryption techniques provided by
the Internet Privacy Enhanced Mall (PEM) message and encryption
authentication procedures. The encrypted random number is stored in a file
as the user's anonymous directory. The server further establishes the
encrypted ASCII representation of the random number as one-time password
for the user. The client workstation initiates an ftp request to obtain
the encrypted PEM random number as a file transfer (ftp) request from the
destination server. The destination server then sends the PEM encrypted
password random number, as an ftp file, over the Internet to the client
workstation. The client workstation decrypts the PEM encrypted file
utilizing the user's private RSA key, in accordance with established PEM
decryption techniques. The client workstation then provides the
destination server with the decrypted random number password, which is
sent in the clear over the Internet, to login to the destination server.
Upon receipt of the decrypted random number password, the destination
server permits the user to login to the anonymous directory, thereby
completing the user authentication procedure and accomplishing login. The
destination server removes the random number password from its anonymous
directory, such that any future login attempts requires a new random
number password. Additionally, the destination server deems the random
number password valid only for a predetermined time period (t), such that
any delay beyond the time period (t) in accomplishing the login by the
client workstation results in a timeout, and invalidation of the random
number password. In the event of a timeout, the user must obtain a new
random number password from the destination server in accordance with the
method of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a work station used to communicate with other
workstations over a network and incorporating the teachings of the present
invention.
FIG. 2 conceptually illustrates the Internet network.
FIG. 3 is a flow chart illustrating the sequence of steps executed by a
user's workstation of the type illustrated in FIG. 1.
FIG. 4 is a flow chart illustrating the sequence of steps for the present
invention's privacy enhanced mail based user authentication system,
executed by a server data processing device.
FIG. 5 is a diagrammatical illustration of the; data paths utilized by the
present invention for providing an encrypted password using privacy
enhanced mail, and the use of the decrypted password sent over the
Internet in accordance with the teachings of the present invention to
accomplish login.
NOTATION AND NOMENCLATURE
The detailed descriptions which follow are presented largely in terms of
symbolic representations of operations of data processing devices coupled
to a network. These process descriptions and representations are the means
used by those skilled in the data processing arts to most effectively
convey the substance of their work to others skilled in the art.
An algorithm is here, and generally, conceived to be a self-consistent
sequence of steps leading to a desired result. These steps are those
requiring physical manipulations of physical quantities. Usually, though
not necessarily, these quantities may take the form of electrical or
magnetic signals capable of being stored, transferred, combined, compared,
displayed and otherwise manipulated. It proves convenient at times,
principally for reasons of common usage, to refer to these signals as
bits, values, elements, symbols, operations, messages, terms, numbers, or
the like. It should be borne in mind, however, that all of these similar
terms are to be associated with the appropriate physical quantities and
are merely convenient labels applied to these quantities.
In the present invention, the operations referred to are machine
operations. Useful machines for performing the operations of the present
invention include general purpose digital computers (referred herein as
"workstations"), or other similar devices. In all cases, the reader is
advised to keep in mind the distinction between the method operations of
operating a computer and the method of computation itself. The present
invention relates to method steps for operating a computer, coupled to a
series of networks, and processing electrical or other physical signals to
generate other desired physical signals.
The present invention also relates to apparatus for performing these
operations. This apparatus may be specially constructed for the required
purposes or it may comprise a general purpose computer selectively
activated or reconfigured by a computer program stored in the computer.
The method/process steps presented herein are not inherently related to
any particular computer or other apparatus. Various general purpose
machines may be used with programs in accordance with the teachings
herein, or it may prove more convenient to construct specialized apparatus
to perform the required method steps. The required structure for a variety
of these machines will be apparent from the description given below.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, numerous details are set forth such as
workstation system configurations, representative messages, servers, etc.,
to provide a thorough understanding of the present invention. However, it
will be apparent to one skilled in the art that the present invention may
be practiced without these specific details. In other instances, well
known circuits and structures are not described in detail in order to not
obscure the present invention. Moreover, certain terms such as "knows",
"sends", "receives", "verifies", "examines", "finds", "determines",
"authenticates", etc., are used in this Specification and are considered
to be terms of art. The use of these terms, which to a casual reader may
be considered personifications of computer or electronic systems, refers,
for simplicity, to the functions of the system as having human-like
attributes. For example, a reference herein to an electronic system as
"determining" something is simply a shorthand method of describing that
the electronic system has been programmed or otherwise modified in
accordance with the teachings herein. The reader is cautioned not to
confuse the functions described with everyday human attributes. These
functions are machine functions in every sense,.
FIG. 1 illustrates a data processing system (hereinafter a "workstation")
in accordance with the teachings of the present invention. The workstation
includes a computer 10 which comprises three major components. The first
of these is an input/output (I/O) circuit 12 which is used to communicate
information in appropriately structured form to and from other portions of
the computer 10. In addition, computer 10 includes a central processing
unit (CPU) 13 coupled to the I/O circuit 12 and a memory 14. These
elements are those typically found in most general purpose computers and,
in fact, computer 10 is intended to be representative of a broad category
of data processing devices. Also shown in FIG. 1 is a keyboard 15 to input
data and commands into computer 10, as is well known. A network interface
circuit 17 is also coupled to the computer 10 through I/O circuit 12, to
permit the computer 10 to communicate with other workstations and servers
over a network, such as for example, the Internet. A raster display
monitor 16 is shown coupled to the I/O circuit 12 and is used to display
images generated by CPU 13 in accordance with the present invention. Any
well known variety of cathode ray tube (CRT) or other type of display may
be utilized as display 16.
Referring now to FIG. 2, the Internet may be conceptually described as an
open network generally referred to in the figure by the numeral 20, to
which numerous servers 22, 24, 26 and 28 are coupled. Each of the
respective servers is coupled to workstations 29, 31, 33 and 35, as shown.
It will be appreciated that FIG. 2 is described for illustration purposes
only, and that in reality the Internet includes many tens of thousands of
servers and work stations. Additionally, although the Internet is
illustrated in FIG. 2 as a single network, it will be appreciated that the
Internet is actually a series of networks forming a spiderweb-like
topology spanning virtually every continent in the world. As is well
known, a user operating a workstation in, for example, Singapore, may send
messages, access data and databases and execute a variety of functions
over the Internet to, for example, a workstation located in Mountain View,
Calif.
In the operation of many networks, and in particular, the Internet, a user
operating for example workstation 29, referred to as the "client
workstation", may wish to access a workstation 33 which, as illustrated,
is coupled to the server 26. The server 26 is referred to in the industry
as the "destination server" and the combination of client workstation 29
and server 26 is known as the "client-server". Generally, in order for
client workstation 29 to access destination server 26 and data which may
be disposed at the server 26, or alternatively, at a workstation 33, it is
necessary for the client workstation 29 to provide a password to the
server 26. However, as previously noted, passwords are sent over the
Internet 20 in "the clear" thereby giving intruders access to unencrypted
passwords. Additionally, passwords are relatively easy to guess given a
sufficiently powerful workstation eavesdropping at a node on the Internet.
Once an unencrypted password has been captured by an intruder the intruder
may then access the network devices as an authorized user. Thus, the
sending of passwords in the clear over the Internet provides an
opportunity for a would be intruder to gain access to an authorized user's
password, and thereby compromises network security.
In accordance with the teachings of the present invention, assume for sake
of example, that a client workstation 29 desires to access a destination
server 26 coupled to the Internet 20. In order to access the destination
server 26 it is necessary for the client workstation 29 to login on the
server 26. The login by the client workstation 29 to server 26 is an
authenticated login in accordance with the teachings of the invention.
Traditionally, the client workstation 29 would simply provide a password
to the destination server 26 in the clear over the Internet 20. However,
for the reasons previously described, the sending of a password in the
clear compromises network security and provides an unacceptable
opportunity for intrusion by third parties. One of the characteristics of
the present invention is that its methodology operates in conjunction with
existing network applications. As previously described, one of the
existing network applications on the Internet is privacy enhancement for
Internet electronic mail (PEM). Each of the servers (in FIG. 1 servers 22,
24, 26 and 28) coupled to the Internet 20 includes PEM, as does each of
the workstations 29, 31, 33 and 35. Generally, PEM is designed to receive
a user name (e-mail address) and to fetch its corresponding public key
certificate. In general, PEM provides public key cryptography for
electronic mail messages, and security for the mail message itself, as
opposed to the authentication of an authorized user. The detailed
operation of privacy enhanced mail will not be described in this
Specification, since it is well established and currently functioning on
the Internet. The reader is referred to the Internet documents,
incorporated by reference herein, entitled "Privacy Enhancement for
Internet Electronic Mail", parts I-IV, (RFC 14.21 through 14.24) for a
detailed description of PEM encryption and authentication procedures. The
present invention will be described herein as it relates to its operation
in conjunction with the existing Internet PEM system. However, it will be
appreciated that the present invention may be used in numerous other
network environments in addition to the Internet.
Referring now to FIGS. 3 and 4 in conjunction with FIG. 5, the operation of
the present invention will be described in further detail. Assume for sake
of example that a client workstation 40 (see FIG. 5) coupled to the
Internet 20 desires to login on a destination server 42. As shown in FIG.
5, the client workstation 40 is coupled to a source server 44, and the
destination server 42 is coupled to at least one workstation 46, as is
common in Internet topology.
As illustrated in the flowchart of FIG. 3, the client workstation 40
through the source server 44 provides a login comprising an anonymous tip,
to the destination server 42. In addition, the client workstation 40
provides a password comprising the user's electronic mail name. The use of
an anonymous ftp provided over the Internet 20 effectively results in a
secure password channel over the Internet. This password is then used to
secure another Internet connection. As illustrated in FIG. 4, the
destination server 42 receives the login request comprising an anonymous
ftp in conjunction with the user's e-mail address as a password. The
destination server 42 compares the client workstation 40 electronic mail
name to its list of authorized users. If the user's electronic mail name
(in the present example, client workstation 40) is not on the list of
authorized users, the client login request is rejected.
If the identified user is on the list of authorized users, then, as
illustrated in FIG. 4, the destination server 42 generates a random number
(X) which will be used as a one-time password. An ASCII representation of
the random number is encrypted using the PEM algorithm, and is placed in a
file in the user's anonymous directory using PEM encrypted message
procedures. As shown in FIG. 4, the destination server 42 establishes the
encrypted ASCII representation of the random number X as the one-time
password for the user.
It will be appreciated that the encrypted random number password is
addressed only to the user operating workstation 40. Only the authorized
user operating workstation 40 can decrypt the encrypted random number
password. As illustrated in the flowchart of FIG. 3, the client
workstation 40 does an ftp to obtain the encrypted PEM random number
password from the destination server 42. The destination server 42 sends
the encrypted PEM random number password to the workstation 40 over the
Internet 20. Although an intruder can detect the encrypted random number
password over the Internet 20, only the authorized user of workstation 40
can decrypt the random number password in accordance with the teachings of
PEM. The workstation 40, using the PEM decryption methodology, decrypts
the encrypted PEM file using the PEM users private RSA key.
The reader is referred to the document, incorporated by reference herein,
by Fahn, "Answers to Frequently Asked Questions about Today's
Cryptography" (RSA Laboratories, 1992), submitted concurrent with the
filing of the application on which this patent is based, and other
references submitted, for a detailed description of RSA technology. Since
the RSA technology is well known, it will not be described further herein.
As shown in the flowchart of FIG. 3, once the PEM encrypted random number
password is decrypted by the client workstation 40 using its private key,
the decrypted password is then supplied over the Internet 20 to the
destination server 42 for login. For the actual login by the client
workstation 40 to the destination server 42, the decrypted random number
password is sent in the clear over the Internet 20 along with the user's
e-mail address name.
As shown in FIG. 4, the destination server 42 permits the user to login to
the anonymous directory utilizing the one-time random number password
within a predetermined time (t). Providing a predetermined time window in
which to permit the client workstation 40 to login to the destination
server 42, provides additional security. In the event the time period (t)
expires without the workstation 40 logging into the destination server 42
utilizing the decrypted random number password, then a time out occurs and
the random number password is deemed invalid. In such event, it is
necessary for the user operating the client workstation 40 to acquire a
new random number password utilizing the teachings described in this
Specification with reference to FIGS. 3 and 4. Assuming that the user
provides the decrypted random number password to the destination server 42
within the time interval (t), the destination server 42 permits the login
and the user authentication process is completed. The destination server
42 then removes the random number X as a password for the user, thereby
requiring any future logins by the workstation 40 to first obtain a new
random number password. Thus, each login between a client and a server
over the Internet requires a new password.
It will be appreciated that since the decrypted random number password
provided by the client workstation 40 to the destination server 42 over
the Internet 20 is sent in the clear, an intruder can detect this password
during the login process. However, since the server 42 invalidates or
removes the random number password after each successful login, or
alternatively, after the time out of the interval (t), network security is
not compromised. Even assuming an intruder intercepts the decrypted random
number password over Internet 20, it is of no use to the intruder since it
is only valid for a single login, and the login must occur during the
predetermined time (t).
Accordingly, a system and method for user authentication in a public
network is disclosed. While the present invention has been described in
conjunction with a few specific embodiments identified in FIGS. 1-5, it
will be apparent to those skilled in the art that many alternatives,
modifications and variations in light of the foregoing description are
possible. For example, although the present invention has been described
with reference to user authentication in the Internet environment, it will
be appreciated that the teachings of the present invention may be applied
to any public or private network topology.
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