Copy indicating security device

Details Copy indicating security device Copy indicating security device

1994-03-18

1995-12-26

Cain, David C.

Cryptography

Cryptanalysis

380 51, 355201, 283 93, 283 94, 283902, H04L 900

Patent

active

054795079

ABSTRACT:
A copy indicating security device includes at least one symbol defined by a first arrangement of print elements, the or each symbol being provided in a background defined by a second arrangement of print elements. Under normal viewing conditions the security device presents a substantially flat tint to the eye. The first and second arrangements of print elements differ from one another so that on copying the device at least one of the symbols is revealed. The perimeter of the or each symbol is generally irregular.

REFERENCES:
patent: 1692405 (1928-11-01), Freeman
patent: 4168088 (1979-09-01), Somlyody
patent: 4175774 (1979-11-01), Tonges et al.
patent: 4227719 (1980-10-01), McElligott et al.
patent: 4341404 (1982-07-01), Mowry, Jr. et al.
patent: 4420175 (1983-12-01), Mowry, Jr.
patent: 4579370 (1986-04-01), Corwin et al.
patent: 5074596 (1991-12-01), Castagnoli
patent: 5197765 (1993-03-01), Mowry, Jr. et al.

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