Patent ID: 11902417
Assignee: PII GUARD APS
Field: Basic communication processes (Electrical engineering)
Classification: CPC H | IPC H

Claim 13:
14. A computer-implemented method for performing format-preserving encryption and decryption of a data object in a first format having predefined format properties, the data object having a variable size, the method comprising:
converting, by use of a first reversible converting algorithm, the data object to obtain a converted version of the data object in a second format;
encrypting the converted version of the data object by use of an inner encryption algorithm and at least one of a tweak and a key, the inner encryption algorithm being capable of taking a variable size input and of outputting, as its output, an encrypted version of the variable size input, to obtain an encrypted version of the data object;
deconverting, by use of a first reversible deconversion algorithm, the encrypted version of the data object to obtain a deconverted encrypted version of the data object in a third format, wherein the combined steps of converting, encrypting, and deconverting are format-preserving such that the third format fulfills the pre-defined format properties of the first format;
outputting the deconverted encrypted version of the data object;
wherein the first deconversion algorithm is different from a reversed version of the first converting algorithm;
wherein the output deconverted encrypted version of the data object in the third format has a different size than the input data object in the first format;
wherein during decryption the data object in the third format is converted into the second format using a second converting algorithm and subsequently decrypted using the same at least one of the tweak and the key used during encryption to obtain a decrypted data object which is subsequently deconverted using a second deconversion algorithm into the first format;
wherein the second deconversion algorithm is an inverse of the first converting algorithm and the first deconversion algorithm is an inverse of the second converting algorithm.