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Having described the invention what is claimed as new and secured by Letters Patent is:
1. Digital logic apparatus for verifying a party, comprising
a memory element for storing an authentication value representative of a password encoded by operation of a one-way commutative function of a base signal representative of a numeric value,
a number generator for generating a number signal,
a processor element coupled to said number generator and to said memory element for generating a key signal representative of said authentication value encoded by operation of said one-way commutative function of said number signal and for
generating a challenge signal representative of said number signal encoded by operation of said one-way commutative function of said base signal,
a communication element for transmitting said challenge signal to said party and for receiving a response signal from said party, and
a comparator element for comparing said response signal with said key signal and for generating a match signal representative of a substantial identity between said key signal and said response signal.
2. Apparatus according to claim 1 wherein said processor element includes means for performing a one-way commutative exponential function modulo a prime number.
3. Apparatus according to claim 1 wherein said number generator includes a random number generator element for generating a sequence of random numbers.
4. Apparatus according to claim 1 wherein said number generator includes a non-repeating number generator element for generating a sequence of non-repeating numbers.
5. Apparatus according to claim 1 wherein said communication port includes error correction means for encoding said challenge signal and decoding said response signal to detect and correct errors that occur in said signals during the transfer of
signals between said apparatus and said party.
6. Apparatus according to claim 1 further comprising means for generating said base signal.
7. Apparatus according to claim 1 wherein said memory element includes means for storing said base signal.
8. Apparatus according to claim 1 further comprising means for generating a prime number signal.
9. Apparatus according to claim 1 wherein said memory element includes means for storing a prime number signal.
10. Apparatus according to claim 1 further comprising means for generating a randomized password signal, including
means for storing a randomizing factor,
means for storing a user selected password signal, and
processor means for digesting said user selected password signal with said randomizing factor for generating said randomized password signal.
11. Apparatus according to claim 1 further comprising digest processor means adapted for digesting said key signal to generated an encrypted key signal.
12. Apparatus according to claim 11 wherein said digest processor means is adapted for implementing an MD5 encryption process.
13. Apparatus for transmitting a secure password signal over a public communication channel, comprising
a server element having
a memory element having storage for an authentication value signal representative of said password signal encoded according to a one-way commutative function,
a non-repeating number generator having an output means and arranged for providing a non-repeating number signal at said output means,
processor element arranged for processing signals according to a one-way commutative function, and coupled to said non-repeating number generator and to said memory element for generating a key signal representative of said authentication value
encoded as a one-way commutative function of said non-repeating number signal and for generating a challenge signal representative of numeric value encoded as a one-way commutative function of said non-repeating number,
a communication port, interfaced to the communication channel, for transmitting said challenge signal and for receiving a response signal, and
a comparator element for comparing said key signal with said response signal and for generating a match signal representative of a substantial identity between said key signal and said response signal,
a client element having
a communication port, interfaced to the communication channel, for receiving said challenge signal and for transmitting said response signal, and
processor element arranged for processing signals according to a one-way commutative function, and coupled to said communication port for generating said response signal as a one-way commutative function of said challenge signal, and said
password signal.
14. Apparatus according to claim 13 wherein said server processor element and said client processor element each includes means for generating a signal according to an exponential function modulo a prime number.
15. Apparatus according to claim 13 wherein said memory element has storage for a plurality of authentication values, each representative of encrypted password signals, and
said processor means is arranged for processing said plurality of authentication values to generate plural key signals and has output means for transmitting each of said key signals to said comparator element for comparison with said response
signal for detecting one of said plural key signals substantially identical to said response signal.
16. Apparatus according to claim 13 wherein said client element further includes a terminal element interfaced with said client processor means and arranged for inputting said password signal to said client processor means.
17. Apparatus according to claim 13 further including a secure database memory element arranged for storing information and having a controller unit coupled to said comparator element for receiving said match signal and for transferring data
between said database memory element and said host communication port responsive to said match signal.
18. Apparatus according to claim 13 further including means for generating a randomized password signal, including
means for storing a randomizing factor,
means for storing a user selected password signal, and
processor means for digesting said user selected password signal with said randomizing factor for generating said randomized password signal.
19. Apparatus according to claim 13 wherein said server element further comprises digest processor means adapted for digesting said key signal to generated an encrypted key signal.
20. Apparatus according to claim 13 wherein said client element further comprises digest processor means adapted for digesting said response signal to generated an encrypted response signal.
21. Method for transmitting a password over a communication channel, said method comprising the steps of
providing a memory element for storing an authentication value signal representative of said password encoded according to a one-way commutative function,
generating a non-repeating number signal,
generating, according to said one-way commutative function, a key signal representative of said authentication value encoded as a one-way commutative function of said non-repeating number signal, and a challenge signal representative of a numeric
value encoded as a one-way commutative function of said non-repeating number signal,
transmitting said challenge signal to a client requesting access to a secure system and receiving a response signal from said client, and
comparing said response signal with said key signal to generate a match signal representative of a substantial identity between said response signal and said key signal.
22. Method according to claim 21 wherein said step of generating a challenge signal includes the step of generating said challenge signal as a one-way commutative function of said numeric value and said non-repeating number signal.
23. Method according to claim 21 wherein said step of providing a memory element adapted to store an authentication value signal includes the step of providing a memory element having a plurality of said authentication value signals, and
generating plural key signals as a one-way commutative function of said plural authentication value signals and said non-repeating number signal.
24. Method according to claim 21 including the further step of accessing data stored in a secure database responsive to said match signal and transferring data between said database and said client.
25. Apparatus for responding to a challenge signal transmitted over a communication, comprising
memory element adapted to store a signal representative of a password signal,
a communication port adapted to interface to the communication channel, for transmitting a response signal, and
processor element arranged for processing signals according to a one-way commutative function, and coupled to said communication port for generating said response signal as a one-way commutative function of said challenge signal, and said
password signal.
26. Method for responding to a challenge signal transmitted over a communication channel, comprising the steps of
storing in a memory element, a signal representative of a password signal,
providing a communication port adapted to interface to the communication channel, for transmitting a response signal,
generating said response signal processor element as a one-way commutative function of said challenge signal, and said password signal, and
transmitting said response signal via said communication port.
27. Apparatus for verifying the identity of a client having a password, said apparatus comprising
a memory element for storing an authentication value, said authentication value being formed by application of a one-way commutative function to a base signal, and to said password,
a processor element configured for generating a challenge signal by application of said one-way commutative function to said base signal and to a number signal, and
a comparator element for comparing a return signal generated by said client, said return signal being generated by application of said one way commutative function to said challenge signal and to said password.
28. Method for verifying the identity of a client having a password, said method comprising the steps of
storing an authentication value, said authentication value being formed by application of a one-way commutative function to a base signal and to said password,
generating a challenge signal by application of said one-way commutative function to said base signal and to a number signal, and
comparing a return signal generated by said client, said return signal being generated by application of said one way commutative function to said challenge signal and to said password. |
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Description |
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FIELD OF THE INVENTION
This invention relates generally to data processing systems and methods that prevent unauthorized access to a restricted area or a device, and more particularly, to data processing systems and methods that employ passwords to verify the identity
of a party requesting access to a restricted area or device.
BACKGROUND OF THE INVENTION
Security systems commonly employ passwords to verify the identity of a party seeking access to a restricted device or area. Commonly, the restricted device is a computer system, such as a file server, that contains classified or other valuable
information. Typically these security systems include a database memory for storing a list of valid passwords, typically indexed before users names, a communication interface that allows a party to transmit a password into the system, and a comparator
element that compares the password entered by the party with the stored list of valid passwords. A match between the offered password and one of the known valid passwords verifies the identity of the party. Alternatively, a failure to match the offered
password with any known valid password causes the security system to deny access to the party.
Generally, these security systems work well to protect communications between a client and sewer. However, the effectiveness of these security systems is predicated upon maintaining the secrecy of all valid passwords. The secrecy of passwords
is subject to breach by at least three methods of attack. In a first method, an interloper breaches security by gaining access to the database memory that contains the stored passwords. The interloper can then capture a valid password and employ the
captured password to gain entry to the server. In a second method of attack an eavesdropper taps into a communication channel that carries data, including valid passwords, between the system and a client. Eventually, the eavesdropper can capture a
valid password and employ this password to access the server. In a third method of attack, an impostor, posing as the security system, dupes an unwitting system client into presenting a valid password. The presented password can be captured, often
without the client ever becoming aware of the deception, and the impostor can gain access to the sewer by presenting the captured password.
In response to this first weakness, cryptographers developed password security systems that have an encryption mechanism for encrypting passwords. The system encrypts the passwords and stores the encrypted passwords in the system database
memory. Typically, the encryption mechanism employs a one way digest function, such as the MD5 digest, to encode each valid password and stores each encoded password in the system database. Consequently, even if an interloper gains access to the
database memory, the passwords are securely encoded and system integrity is maintained. An example of one password security method is the password authentication protocol (PAP) which provides link security under the point-to-point protocol (PPP) as
defined by the Internet Engineering Task Force (IETF). PAP verifies the password offered by a client who requests access to the system. According to this protocol, the system performs the one way digest on each password offered by a client, and
compares the digest of the offered password against each encoded password in the system database. If a match occurs, the system grants the client access to the server. Alternatively, if no match occurs, the system denies the client access to the server
and the server remains protected.
For such a system to work, the client must communicate the password in clear text to the server. Thus, even if the database is secure, the communication port may include an unsecured channel, such as a telephone line, that an eavesdropper can
tap and monitor to capture a password as it is transmitted by the client. If an eavesdropper can capture a valid password, the eavesdropper can present the password to the security system, which will digest the offered password for comparison with the
stored encrypted passwords. Once the security system finds a match, the system grants the eavesdropper access to the server and security is breached.
In response to this problem, cryptographers developed security systems that employ a transmission encryption scheme to secure a public communication channel. Generally, these techniques implement a challenge, response and handshake
authentication method. An example of challenge, response and handshake method is the challenge and handshake authentication protocol (CHAP) defined under the PPP set forth by the IETF. Under CHAP, the system issues a challenge to a client requesting
access. The challenge can be a random number of a certain length, i.e. a certain number of bits. The client typically answers the challenge by performing a one-way function, e.g., a digest, on the random number and on the client's password. The client
transmits the result of this operation back to the system. The system then performs the same one-way function on the random number and on its stored copy of the password (or on each of a number of stored copies of potential passwords). If the system
finds a match between the response of the client and the result of its operation with a valid password, the system grants access to the client. If no match is found, the client is denied access.
As apparent from the foregoing, systems employing a challenge, response and handshake technique secure the communication channel by carrying passwords in an encrypted format. Accordingly, these systems prevent an eavesdropper from capturing a
valid password. However, security systems that employ these techniques are required to maintain a database of plain text passwords to allow the system to check the validity of the response signal sent by the client. Therefore, these systems are at risk
of breach by an interloper who gains access to this database of passwords.
Accordingly, an object of this invention is to provide systems and methods that authenticate the identity of a party and that provide both a secure database of stored passwords and a secure communication channel for transferring passwords.
Still another object of the present invention is to provide systems and methods for authenticating the identity of a party that allows a user to more easily change their password.
These and other objects will become apparent in the description below.
SUMMARY OF THE INVENTION
The invention, in one aspect, provides a method that allows a client to transfer his or her password to a server, while maintaining the secrecy of the client's password. To aid in understanding the following description, certain terms are
defined below. These definitions are not limiting and are only provided to aid in describing the invention recited by the claims.
The term "client", as used herein, encompasses a device or a person and a device that is requesting access to a secure system. For example, a client can be a person having a portable computer and who is trying to establish a telecommunication
link with a secure computer network over a pubic communication path such as a telephone line. Furthermore, the term client can describe a device or a person and a device in which the device communicates by a direct connection or by a wireless exclusive
link, such as an optical or IR link, to a security system that controls and restricts the device's access to information, files, areas, privileges, commands and other system rights.
The term "server", as used herein, encompasses a device that is capable of establishing a communication link with a second device for transmitting, receiving or exchanging information with that second device. As one example, the term server
encompasses an access point on a computer network that is adapted to establish a network link, via a telecommunications channel, with a remote workstation. Moreover, the term server can encompass devices, such as network file servers, that are adapted
to control and restrict a workstation's access to files, information and system rights.
The term "security system", as used herein, can encompass a device or a method that enforces link security for the communication link between the client and the server.
The term "authentication value", as used herein, encompasses a signal that is an encrypted representation of a data value, where the data value is secret. Typically the secret data value is a user password, and accordingly, the authentication
value can be a value employed by the system to authenticate the identity of a user.
The term "one-way function", as used herein, is generally understood, within the art of cryptography, to be a mathematical function F(x, y), where z=F(x, y) and given (x) and (y) it is easy to compute (z), however, given x and z it is infeasible
to compute y. A one-way function is generally considered to be infeasible to invert if the economic cost for determining the operands of the function is greater than the economic value of the information achieved by the inversion. As a practical matter
a function can be considered infeasible to invert if the inversion process requires greater than 10.sup.30 operations.
The term "commutative one-way function" as used herein, is generally understood within the art of cryptography to be a one-way function that exhibits the commutative property. Thus, if F( ) is a one-way function, F( ) is deemed to be a
commutative one-way function if:
The term "non-repeating number", as used herein, encompasses a number, i.e. a numeric value defined by one or more digits, that occurs in a sequence of numbers, which is unlikely to contain any pair of matching numbers. There will, in general,
be some limit to the length of a sequence that can be assumed to contain non-repeating numbers.
The term "random number", as used herein, encompasses a number, i.e. a numeric value defined by one or more digits, that occurs within a sequence of numbers having no specific pattern, such that the probability of any number appearing has no
easily determined relationship to the history of the sequence up to that point, making it difficult to predict subsequent numbers from any point in the sequence. Provided that the appearance of any particular number has a sufficiently low probability, a
random number sequence is also a non-repeating number sequence. Accordingly, all references to non-repeating numbers herein shall be understood to be able to include random numbers.
The method of the invention employs a challenge and response handshake technique that allows a server to authenticate a client based on a password. To this end, the method includes the step of providing the server with a challenge signal
generator, such as a number generator that generates numbers, or electrical signals representative of numbers. The method further includes the step of providing the system with a database of authentication values, or electrical signals representative of
authentication values, where each authentication values corresponds to a valid password.
The system employs the challenge signal generator and the database to implement the handshake. Typically, the handshake technique begins when the client issues an access request to the server. Upon detection of the access request, the system
transmits a challenge signal to the client. The system can generate the challenge signal by selecting a number from a number generator and by using the number to encrypt a base signal, G, by operation of a one-way commutative function, F( ). The
challenge signal generator can include a number generator that generates a sequence non-repeating numbers, a sequence of random numbers, or any other sequence of numbers such that each access request is challenged by a substantially different, or
unpredictable, challenge signal. The encrypted base signal is the challenge signal that the security system issues to the client. In one example, the system encrypts the base number by operation of a one-way commutative function that includes an
exponential function modulo a prime number. This operation can be represented by:
where (C) is the challenge signal, (a) is the selected number, (G) is the base number and (q) is a prime number. The base value G and the prime number q can be preconfigured numbers that are known by both the client and the server and that are
used to generate every challenge signal. Alternatively, either one or both of these values can be separately generated for each password, or a series of passwords, and stored with the corresponding authentication values. The system retrieves and
employs these stored values to generate the challenge signal for a client. The client can maintain stored copies of these values or the server can transmit these values with the challenge signal. Other modifications can be made without departing from
the scope of the invention.
To answer this challenge, the client is required to generate a response signal that indicates that the client knows one valid password. The client can generate this response signal by employing the same one-way commutative function to encrypt
the challenge signal, C, with one valid password. For the above example of an exponential function modulo a prime number, F( ), the correct response is the result of raising the challenge signal by the power of a numeric value representative of a valid
password, modulo the prime number q. This operation can be represented by:
Alternatively, the Response can be written in expanded form as an exponential function of the base number G by the expression:
The client generates the response signal and transfers it to the security system to complete the handshake. The system now verifies if the response indicates that the client knows a valid password. To verify the response, the system retrieves
an authentication value from the authentication value database. Each authentication value in the database represents a password that has been encrypted by operation of the one-way commutative function employed by the system and the client.
Consequently, each authentication value can be represented by:
where (Password) is a password, or a numeric value representing a password, (G) is the base number and (q) is the prime number.
The system generates a key signal to compare the response with the retrieved authentication value. The system generates the key signal by raising the authentication value signal to a power determined by the selected number, a, and determining
the modulus of the result relative to the prime number q. This operation can be represented by:
Given the commutative property of the one-way function, the key signal of Eq. 5 will match the response signal if the password used by the client corresponds to the authentication value selected by the system. This equivalency can be expressed
by:
or for the example function F( ):
The system computes key signals from the authentication values and compares the key signals with the response signal until a match is found or until the entire database has been tested. If a match occurs, the system grants the client access.
Alternatively, if the system fails to find any match in the database, the client has failed to meet the system's challenge and the system denies the client access to the server.
In a further aspect, the invention provides password security systems and devices that include encryption processors adapted to implement an encryption scheme that employs the commutative property of certain one-way mathematical functions. These
systems allow a client and server to exchange a password over a public communication channel without compromising the secrecy of the password.
Generally, these systems include a communication port, an encryption processor and a challenge signal generator that typically comprises a non-repeating number generator. These elements perform the challenge and response method handshake
described above. Each time a client requests access to the server, the communication port detects an access request signal and activates the encryption processor to generate a challenge signal. The encryption processor selects a number from the number
generator and makes one copy for its use and one copy for the client requesting access. The encryption processor employs the non-repeating number to encrypt a base signal by operation of the one-way commutative function and the communication port
transmits the encrypted number as a challenge signal to the client requesting access.
The client receives the challenge signal and employs it to generate a response signal. To this end the client includes a processor that generates the response, termed a logon signal, by encrypting the challenge signal with a password by
operation of the one-way commutative function. One consequence of this technique is that the client generates a new response signal each time the client logs onto the server. In this way, the client changes the encrypted code of the password each time
a response is transmitted over the communication channel. Consequently, the system prevents an eavesdropper on the public communication channel from capturing a bit stream of an encoded password which can be employed in a subsequent access request.
These systems further include a verification system that includes a database of authentication values, an encryption processor and a comparator element. The comparator element can couple to the communication port and can collect the response
signal transmitted from the client. Once the comparator element has received the response signal, the encryption processor reads each authentication value from the database memory and encrypts that signal as a function of the selected non-repeating
number. The processor transmits each encrypted authentication value to the comparator element for comparison with the response signal. A match between two signals indicates that each signal includes the same password and the same non-repeating number.
The system responds to this match to verify the identity of the client.
More specifically, the above described system can include a memory element that stores one or more authentication values that each represent a valid password which has been encrypted by operation of a one-way commutative function. The system
includes a processor element arranged to implement a selected one-way commutative function. Preferably the processor element is arranged to implement a one-way commutative function that includes an exponential-modulo function. The challenge signal
generator can include a random number generator for generating a number in random sequence. The processor element can couple to the random number generator and to the memory element and, by operation of the selected one-way commutative function,
generate a key signal that represents the authentication value encrypted as an exponential-modulo function of the generated random number signal and that further generates a challenge signal that represents a base signal encrypted as an
exponential-modulo function of the random number signal. The system further includes a communication port for transmitting the challenge signal to a party requesting access through the system and for receiving a logon signal from the party that can
include a password offered by the party. The system includes a comparator element that directly compares the logon signal with the key signal and that generates a match signal that represents a substantial identity between the key signal and the logon
signal.
The system thus summarized is particularly useful for verifying the identity of a party requesting access to a secure computing system, such as a computer network file server. Furthermore, the above described system is useful for verifying the
identity of a party requesting access to a computer network from a computer terminal that transmits data, including a password, over an unsecured communication channel, such as a telephone line. As described above, the system can include a database
memory element that stores encrypted passwords in a format that is substantially incapable of decryption. Moreover, the commutative property of the one-way function allows identical signals to be generated by different sequences of the same operations.
This property allows the system to transmit signals in an encrypted format and to compare directly two encrypted signals. Accordingly, this system achieves an apparatus that provides both a secure database memory element and a secure communication
channel.
In a preferred embodiment of the present invention, the encrypted password signals are encoded according to an exponential function modulo a large prime number.
These and other aspects of the invention will become apparent in the following description, when the invention is described and illustrated in connection with the certain preferred embodiments; however, it should be clear that various additions,
subtractions, and modifications can be made by those of ordinary skill in the art without departing from the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the invention may be obtained by reference to the drawings, in which:
FIG. 1 is a functional block diagram of a password security system according to the invention;
FIG. 2 schematically illustrates an alternative embodiment of a system in accord with the invention for verifying the identity of a party; and
FIGS. 3A and 3B are flow chart diagrams illustrating a process in accordance with the invention which employs one-way commutative functions to encrypt passwords.
DESCRIPTION OF ILLUSTRATED EMBODIMENTS
FIG. 1 illustrates the functional components of a system 10 constructed according to the invention for transferring a password between a client and a server. The system 10 illustrated in FIG. 1 includes a database memory element 12, a challenge
signal number generator 14, a processor element 16, and a processor element 20 connected to an optional terminal element 20A and to a communications channel 22 that couples the processor element 20 to both the processor element 16 and the comparator
element 24.
The system 10 implements a challenge and response handshake protocol that employs a commutative one-way function to encrypt the signals that the client and server exchange. The system 10 employs the same one-way commutative function, F(), to
store in the database memory element 12 authentication values 60 that can represent encrypted passwords, or electrical signals representative of encrypted passwords. The password S is a valid password which is assigned to a user that is authorized to
access the server. In the illustrated embodiment, the authentication value 60 is the password encoded into a format that is generally considered infeasible to invert. In a preferred embodiment of the invention, the password S is first randomized to
reduce the system's susceptibility to a dictionary attack. In this preferred embodiment, a randomizing factor, U, is generated at the time the user selects a password P. The client or the server can generate the randomizing factor using any of the
techniques known in the art of cryptography. The server can retain the randomizing factor U and employ this factor each time the user accesses the server, and can include this factor U as part of the challenge signal. Further, the client can retain the
randomizing factor for randomizing the user-selected password each time a response is generated.
One preferred randomizing factor U can be a number of sufficient length, such as a 128 bit or larger number, generated by a random number generator and made available to a processor element that digests the factor U and the selected password S.
In one embodiment of the invention, the processor implements the MD5 algorithm to digest a user selected password and generate a randomized password signal D(S, U). The system 10 employs the randomized password, D(S,U) rather than the password itself as
an input to the commutative function to produce the authentication value 60.
Where S is the randomized password, P is the password selected by the user and U is the randomizing factor.
In operation, the user can access the server by operating the terminal 20A. In particular, the user can enter his or her valid password into the terminal element 20A. The system processor element 16 can detect the request of the client, and
generate a challenge signal 26 that the client must answer to access the server. In the illustrated embodiment, the system 10 generates the challenge signal 26 by accessing the authentication value 60 stored in the database memory 12 and by selecting a
number 32, or a signal representative of a number. As illustrated by the functional block diagram of FIG. 1, the number 32 can be provided by the challenge signal number generator 14 that produces a number signal 32. The number generator 14 can be a
random number generator, a non-repeating number generator, or any other suitable number generator. In the illustrated embodiment, the number 32 is a non-repeating number generated by a non-repeating number generator. The processor element 16 generates
a challenge signal 26 for the client by encrypting a base signal, G, with the number signal 32 by operation of the selected one-way commutative function. The system 10 transmits the challenge signal 26 to the client.
To respond to the challenge signal 26, the client generates a response signal 28 that represents the challenge signal 26 encrypted with the client's password, S. The processor element 20 generates the response signal 28 by operation of the
selected one-way commutative function. As illustrated in FIG. 1, the client transmits the response signal 28 to the comparator element 24. The system 10 generates a key signal 30 by encrypting the authentication value 60 with the non-repeating number
32 by operation of the commutative one-way function. To verify that the client has successfully met the challenge issued by the system, the comparator element 24 compares the key signal 30 with the response signal 28. If the comparator element detects
a match between these two signals 30 and 28, the system 10 grants the client access to the server. Alternatively, if the key signal fails to match the response signal, the system 10 denies the client access to the server.
In a further alternative embodiment, the system 10 can include a processor 16 and a processor 20 that are adapted to implement a second randomizing operation that can add further security to the public communication channel. This second
randomizing operation can include a response signal digest operation, such as an MD5 operation, that encrypts the response signal 28 to generate an encrypted response signal for transmission over a public communication channel. The server employs the
same digest operation to encrypt the key signal 30 to generate an encrypted key signal and the comparator 24 compares these doubly encrypted signals. Both the client and the server can retain or exchange any common encryption keys or other data
necessary for the selected digest operation. A match indicates that the client has met the server's challenge and the system 10 grants access to the client.
FIG. 2 illustrates one embodiment of the security system 10 constructed as part of a file server that has a database element 40 which stores files and other information. The file server is part of a host element 44 connected via a communication
channel 22, to a client element 46. The illustrated host element 44 includes a memory element 12, a random number generator 14, a processor element 16, a communication port 18, a comparator element 24 and a database element 40 having a database control
element 42. As depicted in FIG. 2, the client element 46 connects to the host element 44 via the communication channel 22 that connects between the communication port 18 and a communication port 48.
The system 10, depicted in FIG. 2, is arranged for transferring passwords in an encrypted format over a public communication channel such as the communication channel 22. In this aspect of the invention, the communication channel 22 represents
an insecure communication channel such as a telephone line, computer network, or other non-secure communication link. To this end, the system 10, depicted in FIG. 2, includes the communication ports 18 and 48, the random number generator 14, the memory
element 12 and the processors 16 and 50, all of which are arranged as a communication interface that transfers a password as part of a randomly generated signal. The randomly generated signal encodes a valid password in an encrypted format that is
generally considered infeasible to invert. Further, this encrypted string is randomly generated each time a password is transferred over the public communication channel 22. Consequently, an interloper eavesdropping on the channel 22 can only capture
the password as part of a generated string that is randomly produced for this single transfer. As such, the randomly encrypted value fails to provide general access to the system 10. From the above description, one of ordinary skill in the art is to
recognize that the present invention can be practiced with a communication channel 22 that is generally considered secure against interlopers.
The database memory element 12, processor 16 and comparator element 24 form a verification system that can verify the identity of a party requesting access to the system by directly comparing the randomly encrypted value sent by the client 46
against a value generated by the processor 16. As such, the system 10 provides a verification system that can directly compare two signals, each of which can be in an encrypted format, to verify the identity of a party seeking access onto the system.
Consequently, the system 10 can include the database memory element 12 that stores authentication values 60A-60D in an encrypted format that is generally considered infeasible to invert.
In the illustrated embodiment, the database memory 12 has storage registers for storing a plurality of authentication values 60A-60D. Each authentication value 60A-60D can represent a plain text password that has been encrypted into a cipher
text format. As is generally known in the art of cryptography, plain text is information written in a format that is clearly understood in the present format. Alternatively, cipher text is a message or information written in a format not understood
without changing the format of the information. In a preferred embodiment of the invention, the authentication value signals 60A-60D are encrypted according to a one-way commutative function that is infeasible to invert. Within the field of
cryptography, a cipher signal is generally considered to be infeasible to invert if the cost as measured by either the amount of memory used or the computing time is finite but impossibly large, for example, on the order of approximately 10.sup.30
operations, with existing computational methods and equipment.
In the illustrated system 10, the memory element 12 includes a storage element 62 that can store a base signal 64 and a prime signal 66 that are suitable for use with a commutative one-way function that includes an exponential-modulo function.
Such functions, which are well known within the art of cryptography, generally include a base signal, such as signal 64, that is raised to the power of a secure signal such as a password, and that is modulo a prime number, such as the prime number
represented by signal 66. Generally, such functions are represented by
where (C) is the encrypted product of the operation, (G) is the base signal 64 and (q) is the prime numbe | | |
