US5440635A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cryptographic protocol for remote authentication
Assignee: AT&T Inc
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Filing: 1993-08-23
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Granted: 1995-08-08
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Expires: 2013-08-23
Abstract
Abstract A cryptographic communication system is disclosed which permits computer users to authenticate themselves to a computer system without requiring that the computer system keep confidential the password files used to authenticate the respective user's identities. The invention is useful in that it prevents a compromised password file from being leveraged by crafty hackers to penetrate the computer system.
Inventors
- 👤 Steven M. Bellovin
- 👤 Michael J. Merritt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 03:30
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/08; H04L9/0816; H04L9/0838; H04L9/0841; H04L9/0844
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
167 words
A method for generating a first cryptographic key to a first symmetric key cryptosystem, said method comprising: generating an authentication signal, D A , that is not revealed to a remote party; generating a first one-way function of said authentication signal, E A ; transmitting said first function of said authentication signal, E A , to said remote party; forming an excitation signal based on a first signal, R A ; forming an outgoing signal by encrypting at least a portion of said excitation signal with a second symmetric key cryptosystem and a second key that is based on said first function of said authentication signal; transmitting said outgoing signal to said remote party; receiving a response signal, Q, in response to said outgoing signal; generating said first cryptographic key based on said first signal and on said response signal; generating a validation signal based on a second function of said first cryptographic key and said authentication signal; and transmitting said validation signal to said remote party.
Claim 2
Independent Claim
167 words
A method for generating a first cryptographic key to a first symmetric key cryptosystem, said method comprising: generating an authentication signal, D A , that is not revealed to a remote party; generating a first one-way function of said authentication signal, E A ; transmitting said first function of said authentication signal, E A , to said remote party; forming an excitation signal based on a first signal, R A ; forming an outgoing signal by encrypting at least a portion of said excitation signal with a second symmetric key cryptosystem and a second key that is based on said first function of said authentication signal; transmitting said outgoing signal to said remote party; receiving a response signal, Q, in response to said outgoing signal; generating said first cryptographic key based on said first signal and on said response signal; generating a validation signal based on a second function of said first cryptographic key and said authentication signal; and transmitting said validation signal to said remote party.
Claim 3
Dependent Claim
35 words
The method of claim 1 further comprising the step of encrypting at least a portion of said validation signal with a third symmetric key cryptosystem and a third key based on said first cryptographic key.
Claim 4
Dependent Claim
24 words
The method of claim 2 wherein said first symmetric key cryptosystem, said second symmetric key cryptosystem, and said third symmetric key cryptosystem are identical.
Claim 5
Dependent Claim
32 words
The method of claim 1 wherein said step of forming an excitation signal comprises the step of setting said excitation signal to α R .sbsp.A moduloβ, where α and β are numbers.
Claim 6
Dependent Claim
29 words
The method of claim 4 wherein said step of generating a first cryptographic key comprises the step of setting said first cryptographic key to Q R .sbsp.A mod β.
Claim 7
Dependent Claim
13 words
The method of claim 1 wherein said second function is a one-way function.
Claim 8
Dependent Claim
21 words
The method of claim 1 wherein said first function is a hash function and said second function is a hash function.
Claim 9
Dependent Claim
14 words
The method of claim 1 wherein said second function is a digital signature function.
Claim 10
Independent Claim
132 words
A method for generating a first cryptographic key to a first symmetric key cryptosystem, said method comprising: receiving a public key to a public key cryptosystem; receiving an outgoing message from a remote party: decrypting said outgoing message with said public key to recover an excitation signal, Q; forming response signal based on a first signal, R B ; encrypting said response signal with a second key based on said public key to form an incoming signal; transmitting said incoming signal to said remote party; generating said first cryptographic key based on said first signal, R B , and on said excitation signal; receiving a validation signal that is based on a second function of said first cryptographic key and said public key; and verifying said validation signal with said public key.
Claim 11
Independent Claim
132 words
A method for generating a first cryptographic key to a first symmetric key cryptosystem, said method comprising: receiving a public key to a public key cryptosystem; receiving an outgoing message from a remote party: decrypting said outgoing message with said public key to recover an excitation signal, Q; forming response signal based on a first signal, R B ; encrypting said response signal with a second key based on said public key to form an incoming signal; transmitting said incoming signal to said remote party; generating said first cryptographic key based on said first signal, R B , and on said excitation signal; receiving a validation signal that is based on a second function of said first cryptographic key and said public key; and verifying said validation signal with said public key.
Claim 12
Dependent Claim
31 words
The method of claim 9 further comprising decrypting at least a portion of said validation signal with a third symmetric key cryptosystem and a third key based on said cryptographic key.
Claim 13
Dependent Claim
24 words
The method of claim 9 wherein said first symmetric key cryptosystem, said second symmetric key cryptosystem, and said third symmetric key cryptosystem are identical.
Claim 14
Dependent Claim
32 words
The method of claim 9 wherein said step of forming an response signal comprises the step of setting said excitation signal to α R .sbsp.B modβ, where α and β are numbers.
Claim 15
Dependent Claim
26 words
The method of claim 12 wherein said step of generating a cryptographic key comprises the step of setting said cryptographic key to Q R .sbsp.B modβ.
Claim 16
Dependent Claim
13 words
The method of claim 9 wherein said second function is a one-way function.
Claim 17
Dependent Claim
21 words
The method of claim 9 wherein said first function is a hash function and said second function is a hash function.
Claim 18
Dependent Claim
14 words
The method of claim 9 wherein said second function is a digital signature function.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-08-07 | 1999-02-06 | 1999-08-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-08-07 | 2003-02-06 | 2003-08-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-08-07 | 2007-02-06 | 2007-08-08 | $7700.00 | Window Closed / Lapsed |