Patent ID: 8756413

Claim:
A method for ensuring information integrity and non-repudiation over time, said method comprising: creating, by a computing device, a key history, associating a brand identity with said key history and acquiring an administrative key pair, which is a pair of cryptographic keys containing a public key and a private key associated with said key history and brand identity and which pair is used for administrating the key history; adding, if a further key pair is to be used representing the brand identity associated with the key history, a copy of a public key of the further key pair to said key history together with an associated start time from which said further key pair will be used, calculating a hash value based on the added public key and the start time, encrypting the hash value with a private key of an administrative key pair, associating the encrypted hash value with said further key pair and adding the encrypted hash value to the key history; adding, if a key pair representing the brand identity should cease to be used, an end time from which the key pair should cease to be used to said key history, associating it with a public key of the key pair that should cease to be used and calculating a hash value based on the public key of the key pair that should cease to be used and the end time, encrypting the hash value with a private key of an administrative key pair, associating the encrypted hash value with said end time and adding it to the key history; associating an information set with a time stamp, calculating a hash value based on the information set and the time stamp, encrypting the hash value with a private key of an enlisted key pair valid at the time of said time stamp, wherein an enlisted key pair valid at a certain time is a key pair of which a public key copy is added to said key history with an associated start time that is earlier than said certain time and where there is no end time associated with the enlisted public key in the key history, or there is an end time associated with the enlisted public key that is later than said certain time, the information set including information used for integrity and non-repudiation verification; and associating said information set, its associated time stamp, the encrypted hash value of the information set and a public key copy of the enlisted key pair of which the private key was used to encrypt the hash value.