Patent US5394471A successfully refreshed from Google Patents.
US5394471A
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Method and system for proactive password validation
Assignee: Verizon Patent and Licensing Inc
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Filing: 1993-09-17
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Granted: 1995-02-28
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Expires: 2013-09-17
Abstract
Abstract An improved method for password validation comprising the steps of identifying bad passwords having one or more characters; computing a frequency of occurrence of bad password characters; computing a probability of occurrence T of the bad password characters within the bad passwords based upon the computed frequency of occurrence; identifying a proposed password having one or more characters; and comparing the proposed password characters with the probability of occurrence T of the bad password characters. The method further comprises the steps of establishing a validation threshold and validating the proposed password based upon the correspondence between (i) a value, BAp, reflecting the relationship between the probability of occurrence T of bad password characters within bad passwords and the proposed password characters and (ii) an established validation threshold. A Markov model is use to compute the probability of occurrence. The present invention also includes an improved password validation system.
Inventors
- 👤 Ravi Ganesan
- 👤 Christopher I. Davies
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:24
CPC Classifications
G; G06; G06F; G06F21/00; G06F21/30; G06F21/45; G06F21/46
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
93 words
An improved method for password validation comprising the steps of: (a) identifying bad passwords, wherein each said bad password is comprised of one or more characters; (b) computing a frequency of occurrence of said bad password characters; (c) computing a probability of occurrence T, within said bad passwords, of the bad password characters using the computed frequency of occurrence; (d) identifying a validation password, wherein said validation password is comprised of one or more characters; and (e) comparing said validation password characters with the probability of occurrence T of the bad password characters.
Claim 2
Dependent Claim
93 words
An improved method for password validation comprising the steps of: (a) identifying bad passwords, wherein each said bad password is comprised of one or more characters; (b) computing a frequency of occurrence of said bad password characters; (c) computing a probability of occurrence T, within said bad passwords, of the bad password characters using the computed frequency of occurrence; (d) identifying a validation password, wherein said validation password is comprised of one or more characters; and (e) comparing said validation password characters with the probability of occurrence T of the bad password characters.
Claim 3
Dependent Claim
126 words
An improved method for password validation according to claim 1, further comprising the steps of (i) computing a first set of log likelihood functions 11f 1 for the bad password characters using the computed probability of occurrence T; (ii) computing a mean μ and standard deviation σ for said first set of log likelihood functions 11f 1 ; and (iii) computing a second set of log likelihood functions 11f 2 for the validation password characters using the computed probability of occurrence T; wherein in the comparing step the probability of occurrence T of the bad password characters is represented by the mean μ and the standard deviation σ and the validation password characters are represented by said second set of log likelihood functions 11f 2 .
Claim 4
Dependent Claim
67 words
An improved method for password validation according to claim 2, wherein said step of comparing is comprised of the steps of (i) computing BAp using the equation ##EQU6## where l-x is a numeric value related to the number of validation password characters; (ii) establishing a validation threshold value; and (iii) accepting or rejecting said validation password based upon the correspondence between BAp and the validation threshold value.
Claim 5
Dependent Claim
17 words
An improved method for password validation according to claim 3, wherein the validation threshold value is -2.6.
Claim 6
Dependent Claim
33 words
An improved method for password validation according to claim 3 further comprising the step of electronically storing the means μ, the standard deviation σ, the probability of occurrence T and the threshold valve.
Claim 7
Dependent Claim
37 words
An improved method for password validation according to claim 3, wherein the steps of computing the set of log likelihood functions 11f 2 and BAp and accepting or rejecting the validation password are performed in real time.
Claim 8
Dependent Claim
35 words
An improved method for password validation according to claim 1, wherein the step of computing the probability of occurrence T is performed using a Markov model comprised of a common alphabet plus selected other characters.
Claim 9
Dependent Claim
19 words
An improved method for password validation according to claim 7, wherein said Markov model is a second order model.
Claim 10
Dependent Claim
23 words
An improved method for password validation according to claim 7, wherein said common alphabet plus selected other characters is comprised of twenty-eight characters.
Claim 11
Dependent Claim
24 words
An improved method for password validation according to claim 1, wherein said bad password characters and said validation password characters are formed into trigrams.
Claim 12
Dependent Claim
58 words
An improved method for password validation according to claim 10, wherein said sets of log likelihood functions are computed using the equation ##EQU7## where 1-2 is a numeric value corresponding to the number of trigrams formed by the validation password characters and P i , P i+1 and P i+2 represent the validation password characters forming a trigram.
Claim 13
Dependent Claim
27 words
An improved method for password validation according to claim 11, further comprising the step of adjusting the frequency of occurrence of certain of the bad password characters.
Claim 14
Dependent Claim
33 words
An improved method for password validation according to claim 12, wherein the step of adjusting the frequency of occurrence includes setting to zero each frequency of occurrence having a value equal to 1.
Claim 15
Dependent Claim
38 words
An improved method for password validation according to claim 13, wherein the step of adjusting the frequency of occurrence further includes the adjustment of each frequency of occurrence having a value of less than or equal to five.
Claim 16
Dependent Claim
67 words
An improved method for password validation according to claim 14, wherein the step of adjusting each frequency of occurrence with a value of less than or equal to five is performed using the equation ##EQU8## where f[i,j,k] is the frequency of occurrence of a trigram of the bad password characters and R is an array representing how often a particular one of the bad password characters occurs.
Claim 17
Dependent Claim
107 words
An improved password validation system comprising: (a) means for accessing a data base of bad passwords, wherein each said bad password is comprised of one or more characters; (b) means for computing a frequency of occurrence of said bad password characters; (c) means for computing a probability of occurrence T, within said bad passwords, of the bad password characters using the computed frequency of occurrence; (d) means for inputting a validation password to the system, wherein said validation password is comprised of one or more characters; and (e) comparitor means for comparing said validation password characters with the probability of occurrence T of the bad password characters.
Claim 18
Dependent Claim
107 words
An improved password validation system comprising: (a) means for accessing a data base of bad passwords, wherein each said bad password is comprised of one or more characters; (b) means for computing a frequency of occurrence of said bad password characters; (c) means for computing a probability of occurrence T, within said bad passwords, of the bad password characters using the computed frequency of occurrence; (d) means for inputting a validation password to the system, wherein said validation password is comprised of one or more characters; and (e) comparitor means for comparing said validation password characters with the probability of occurrence T of the bad password characters.
Claim 19
Dependent Claim
125 words
An improved password validation system according to claim 16, further comprising (i) means for computing a first set of log likelihood functions 11f 1 for the bad password characters using the computed probability of occurrence T; (ii) means for computing a mean μ and standard deviation σ for said first set of log likelihood functions 11f 1 ; and (iii) means for computing a second set of log likelihood functions 11f 2 for the validation password characters using the computed probability of occurrence T; wherein the comparitor means utilizes the mean μ and the standard deviation σ to represent the probability of occurrence T of the bad password characters, and the second set of log likelihood functions 11f 2 to represent the validation password characters.
Claim 20
Dependent Claim
69 words
An improved password validation system according to claim 17, wherein said comparitor means is comprised of (i) means for computing BAp which implements the equation ##EQU9## where l-x is a numeric value related to the number of validation password characters; (ii) means for accessing a validation threshold value; and (iii) means for accepting or rejecting said validation password based upon the correspondence between BAp and the validation threshold value.
Claim 21
Dependent Claim
16 words
An improved password validation system according to claim 18, wherein the validation threshold value is -2.6.
Claim 22
Dependent Claim
69 words
An improved password validation system according to claim 18, wherein, the validation password characters are in the form of trigrams and said means for computing sets of log likelihood functions implements the equation ##EQU10## where 1-2 is a numeric value corresponding to the number of trigrams formed by the validation password characters and P i , P i+1 and P i+2 represent the validation password characters forming a trigram.
Claim 23
Dependent Claim
25 words
An improved password validation system according to claim 20, further comprising means for adjusting the frequency of occurrence of certain of the bad password characters.
Claim 24
Dependent Claim
31 words
An improved password validation system according to claim 21, wherein the means for adjusting the frequency of occurrence sets to zero each frequency of occurrence having a value equal to 1.
Claim 25
Dependent Claim
34 words
An improved password validation system according to claim 22, wherein the means for adjusting the frequency of occurrence further adjusts each frequency of occurrence having a value of less than or equal to five.
Claim 26
Dependent Claim
63 words
An improved password validation according to claim 23, wherein the means for adjusting each frequency of occurrence with a value of less than or equal to five implements the equation ##EQU11## where f[i,j,k] is the frequency of occurrence of a trigram of the bad password characters and R is an array representing how often a particular one of the bad password characters occurs.
Claim 27
Dependent Claim
40 words
An improved password validation system according to claim 18, wherein the means for computing the set of log likelihood functions 11f 2 and BAp and the means for accepting or rejecting the validation password perform on-line and in real time.
Claim 28
Dependent Claim
32 words
An improved password validation system according to claim 25, further comprising means for electronically storing the mean μ, the standard deviation σ, the probability of occurrence T and the validation threshold valve.
Claim 29
Dependent Claim
19 words
An improved password validation system according to claim 26, wherein said electronic storage means resides in a central server.
Claim 30
Dependent Claim
21 words
An improved password validation system according to claim 27, wherein said server is part of a local or wide area network.
Claim 31
Dependent Claim
41 words
An improved password validation system according to claim 18, wherein said means for computing the set of log likelihood functions 11f 2 and BAp and said means for accepting or rejecting the validation password are part of a central security processor.
Claim 32
Dependent Claim
32 words
An improved password validation system according to claim 16, wherein the means for computing the probability of occurrence T utilizes a Markov model comprised of a common alphabet plus selected other characters.
Claim 33
Dependent Claim
18 words
An improved password validation system according to claim 30, wherein said Markov model is a second order model.
Claim 34
Dependent Claim
22 words
An improved password validation system according to claim 30, wherein said common alphabet plus selected other characters is comprised of twenty-eight characters.
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) | 1998-02-27 | 1998-08-29 | 1999-02-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-02-27 | 2002-08-29 | 2003-02-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-02-27 | 2006-08-29 | 2007-02-28 | $7700.00 | Window Closed / Lapsed |