Patent ID: 9275241
Filing Date: 2016-03-01
CPC Classification: G06F,H04L

Claim Text:
1. A cryptographic method between a portable data carrier and a terminal device using a public terminal key and a secret terminal key of the terminal device, the method comprising: in the portable data carrier, storing an authentication parameter, a public data-carrier key of the portable data carrier and a secret data-carrier key of the portable data carrier, wherein the public data-carrier key is a static public group key, and wherein the secret data-carrier key is a key unique for the portable data-carrier, the secret data-carrier key being derived from a secret group key, the secret group key and the static public group key being a group key pair, and in the portable data carrier, signing or encrypting a session parameter by means of the stored authentication parameter to enable a checking of a terminal supplied authentication parameter, being supplied to the terminal device via user input or via optical reading from the portable data carrier, wherein the public data-carrier key is determined by exponentiating a specified primitive root by the secret basic key, the secret data-carrier key is formed by multiplying the secret basic key by a first random number, and a first base value is formed by exponentiating the primitive root by the reciprocal of the first random number, and wherein a secret data-carrier session key of the portable data carrier is determined by multiplying the secret data-carrier key by the session parameter, and a session base is formed by exponentiating the first base by the reciprocal of the session parameter, the session parameter being specified by a second random number or a parameter of the terminal device, and the secret data-carrier key being replaced by the secret data-carrier session key, and the first base by the session base.