Method and device for authenticating a visual item
AssigneeSicpa Holding SA
InventorCheng CHEN
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Abstract
The present invention relates to the technical field of optical detection of the authenticity or non-authenticity of visual items Particularly, the invention relates to the technical field of respectively encryption methods and authentication methods of a digital representation of a visual item using respectively an encryption device and an authentication device.
Claims16
A method for authenticating a visual item VI using a stored digital fingerprint F0 and an authentication device AD, said authentication device AD comprising at least one optical unit OPT1 and at least one processing unit CPU1, said stored digital fingerprint F0 being previously generated from an authentic visual item AVI, said method comprising the following steps:
- a) acquiring, using said optical unit OPT1, at least a plurality of images I of an area comprising the visual item VI to be authenticated, said optical unit OPT1 being in communication with said processing unit CPU1, each image It of the plurality of images I comprising at least partially one digital representation of said visual item VI, the image It being acquired at a time t;
- and b) for each image It of the plurality of images I, generating, by said processing unit CPU1, a spatially corrected image Ict by correcting the image It based on at least one spatial feature to calibrate the at least partially one digital representation of said visual item VI to be in a same perspective as that of said authentic visual item AVI, creating a plurality of spatially corrected images Ic;
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- c) for each spatially corrected image Ict of the plurality of spatially corrected images Ic:
- i) extracting, by said processing unit CPU1, a plurality of features;
- and
- ii) generating, by said processing unit CPU1, a digital fingerprint Ft of the digital representation of the visual item VI from the spatially corrected image Ict using at least a portion of said extracted plurality of features;
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- iii) calculating, by said processing unit CPU1, at least one distance metric D(Ict) between said digital fingerprint Ft and said stored digital fingerprint F0;
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- iv) calculating, by said processing unit CPU1, a first likelihood function L(Ict|H) of authenticity H of the visual item VI from its digital representation from the spatially corrected image Ict based on said calculated distance metric D(Ict) and a second likelihood function L(Ict|G) of non-authenticity G of the visual item VI from its digital representation from the spatially corrected image Ict based on said calculated distance metric D(Ict);
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- v) computing, by said processing unit CPU1, a probability P(H) that the visual item VI is authentic using the first likelihood function L(Ict|H) and the second likelihood function L(Ict|G);
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- wherein the probability P(H) is updated as each spatially corrected image Ict of the plurality of spatially corrected images is processed, and the authentication of the visual item VI is confirmed, by said processing unit CPU1, if the probability P(H) is greater than a predetermined threshold.
An authentication device AD configured to authenticate a visual item VI using a stored digital fingerprint F0, said stored digital signature F0 being previously generated from an authentic visual item VI, said authentication device AD comprising:
- a) an optical unit OPT1 configured to acquire at least a plurality of images I of an area comprising the visual item VI to be authenticated, each image It of the plurality of images I comprising at least partially one digital representation of said visual item VI, the image It being acquired at a time t;
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- b) a processing unit CPU1 configured to:
- i) for each image It of the plurality of images I, generate a spatially corrected image Ict by correcting the image It based on at least one spatial feature to calibrate the at least partially one digital representation of said visual item VI to be in a same perspective as that of said authentic visual item AVI, creating a plurality of spatially corrected images Ic;
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- ii) for each spatially corrected image Ict of the plurality of spatially corrected images Ic:
- (1) extract a plurality of features;
- and
- (2) generate a digital fingerprint Ft of the digital representation of the visual item VI from the spatially corrected image Ict using at least a portion of said extracted plurality of features;
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- (3) calculate at least one distance metric D(Ict) between said digital fingerprint Ft and said stored digital fingerprint F0;
- and
- (4) calculate a first likelihood function L(Ict|H) of authenticity H of the visual item VI from its digital representation from the spatially corrected image Ict based on said calculated distance metric D(Ict) and a second likelihood function L(Ict|G) of non-authenticity G of the visual item VI from its digital representation from the spatially corrected image Ict based on said calculated distance metric D(Ict);
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- (5) compute a probability P(H) that the visual item VI is authentic using the first likelihood function L(Ict|H) and the second likelihood function L(Ict|G), the probability P(H) being updated as each spatially corrected image Ict of the plurality of spatially corrected images is processed;
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- (6) confirm that the visual item VI is authentic if the probability P(H) is greater than a predetermined threshold.
A digital fingerprint generation device GD configured to generate a digital signature F0 from an authentic visual item AVI, said digital fingerprint F0 being configured to be stored, said digital signature generator device GD comprising:
- a) an optical unit OPT2 configured to acquire at least one image I of the authentic visual item AVI and/or a download unit configured to download at least one image I of the authentic visual item AVI from at least one server;
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- b) a processing unit CPU2 configured to:
- i) generate a spatially corrected image Ic by correcting the image I based on at least one spatial feature;
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- ii) extract a plurality of features from said spatially corrected image Ic;
- and
- iii) generate the digital fingerprint F0 of the digital representation of the authentic visual item VI from the spatially corrected image Ic using at least a portion of said extracted plurality of features.
Dependencies are inferred from the claim text.