Browse Prior Art Database

Pen Lift Eliminator

IP.com Disclosure Number: IPCOM000083472D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 4 page(s) / 41K

Publishing Venue

IBM

Related People

Evangelisti, CJ: AUTHOR [+2]

Abstract

There exists a need for security devices to guarantee that persons seeking access to buildings, computer terminals, etc., are who they claim to be. Using signatures as a means of verifying a person's identity is an attractive method, since signatures are already used as a means of verification. It does not require an object which may be lost or forgotten. It does not have the unpleasant connotations that other methods such as fingerprints might have. Using the dynamics (e.g., acceleration) of how a person writes his name is even more attractive, because a forger does not have easy access to such information.

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Pen Lift Eliminator

There exists a need for security devices to guarantee that persons seeking access to buildings, computer terminals, etc., are who they claim to be. Using signatures as a means of verifying a person's identity is an attractive method, since signatures are already used as a means of verification. It does not require an object which may be lost or forgotten. It does not have the unpleasant connotations that other methods such as fingerprints might have. Using the dynamics (e.g., acceleration) of how a person writes his name is even more attractive, because a forger does not have easy access to such information.

The acceleration waveforms obtained from an outline pen can be used as a means of comparing two signatures. In comparing the waveforms of two signatures by the same person, misregistrations are often seen. For example, the waveforms will match at the beginning but not elsewhere. Shifting one of the waveforms causes the middle to match but not the ends. A solution to this problem is to use the information available when the signer lifts or drops his pen, as a means of registering parts of a signature.

A Sylvania Tablet has been used to gather data for signatures. Limited information about the pen position in the Z direction (as well as X and Y) is available. During a number of experiments, it was found that the number of pen lifts in a signature was not consistent for a given signer. The signer would often graze the paper when he crossed a t or dotted an i. This grazing was at the threshold for determining if the pen was up or down. Also the signer would be inconsistent in dotting i's, etc. The solution to this problem is the pen-lift eliminator which is being disclosed.

If a master signature is compared to an unknown signature and the number of pen lifts in each signature is different, the eliminator will eliminate pen lifts from the signature having more pen lifts. Determining which pen lifts are to be removed is the function of the eliminator. The eliminator will first remove pen lifts to make the number of pen lifts in each signature the same. After the pen lifts have been removed, the eliminator may eliminate an additional pair of pen lifts, one from each signature. This will take place if it is decided that the pair of pen lifts do not occur in the same part of the signature.

The algorithm for eliminating pen lifts uses a distance measure (DIS) to compare two signatures. A vector for each signature is generated. Each entry in the vector represents the number of sample points (the duration of time) between pen lifts. (The number of pen lifts in each signature must be the same when calculating the distance.) If the number of pen lifts in each signature is N, then the number of entries in the vector is N+1. It is assumed there are no pen lifts at the beginning or end of the signature. The distance measure is defined as: DIS = (al-bl)**2+ (a2-b2)**2+ ... +(az-bz)**2 where a and b are the two different sign...