Patent ID: 8670562

Claim:
A control process in a control system comprising a control device adapted to receive a signal indicating a first biometric data item (w) and to obtain a second captured biometric data item (w′), said process comprising the following steps at the control device: /a/ comparing the first and second biometric data items, /b/ deciding that the first and second biometric data items correspond to each other on the basis of step /a/, and /c/ generating at least a portion (K) of a secret cryptographic key (H(w)) by applying a cryptographic function (H) to the first biometric data item, wherein a group secret (γ) is associated with members of a group, each of the members being able to do a group signature; said process additionally comprising the following steps at the control device: /i/ receiving a message (M), /ii/ signing the message on the basis of the secret cryptographic key (H(w)) comprising the secret cryptographic key portion (K) generated in step /c/ and another secret cryptographic key portion (A), wherein the another secret cryptographic key portion (A) satisfies the following equation: A=g 1 1/(K+γ) where g 1 is a public parameter of the control system, and /iii/ sending the signed message (σ) in response to step /i/.