Patent ID: 8214642

Claim:
A method for distribution of a set of credentials from a credential issuer to a credential user, wherein the credential user is provided with a user device, wherein a first channel and a second channel are provided for communication between the user device and the credential issuer, the method comprising the steps of: distributing a shared key between the user device and the credential issuer by means of the second channel; generating a binary representation of the set of credentials with a predefined maximum level of deviation from a uniform distribution by: (i) generating a first representation of the set of credentials with a first level of randomness, wherein the first level of randomness corresponds to a first level of deviation from a uniform distribution; (ii) transforming the first representation into a second representation of the set of credentials with a second level of randomness, wherein the second level of randomness is higher than the first level of randomness and corresponds to a second level of deviation from a uniform distribution, and wherein the second level of deviation from a uniform distribution is lower than the first level of deviation from a uniform distribution; and (iii) transforming the second representation of the set of credentials into the binary representation with the predefined maximum level of deviation from a uniform distribution; encrypting the binary representation of the set of credentials by means of the shared key; distributing the encrypted set of credentials via the first channel from the credential issuer to the user device; and decrypting the encrypted set of credentials by the user device by means of the shared key, wherein the predefined maximum level of deviation from a uniform distribution of the binary representation of the set of credentials is determined by a predefined security level, key-lengths of the shared key and the predefined number of verification trials; wherein a message M being a sequence of credential symbols over the credential alphabet A: A={a1, . . . , ak} credential alphabet with k credential symbols, k>=1 w=s1|s2| . . .| sj word constructed by concatenating j credential symbols s, s element A, j>=1; each word represents a credential; W=(w1, . . . , wq) set of q words, q>=1, establishing a set of credentials; and M=w1| . . . | wq message consisting of n credential symbols s, s element A, n =sum(q=1,q)j(wq).