Abstract: A method for providing a public key/secret key pair for encrypting and decrypting data, wherein the public key of the public key/secret key pair and a master secret key are generated based on predefined policy information, and wherein the secret key of the public key/secret key pair is generated based on the generated master secret key and predefined attribute information. A method for accessing a system in an untrusted environment and a system for providing a public key/secret key pair for encrypting and decrypting data as well as a use for access control are also described.

Abstract: A method for providing encrypted data for searching of information includes generating a number of distinct key triples each comprising a public key, a corresponding secret key, and a corresponding evaluation key based on searchable information and files to be searched. Information indicating whether the searchable information is included within the files is encrypted with a key of the generated key triples. The secret keys are merged to obtain a single secret key for an entirety of the searchable information within respective ones of the files for each of the files. The encrypted information is provided with the merged secret keys for each of the files as encrypted data for searching of information within the files. The generating of the distinct key triples and the encrypting of the information are performed based on a multikey homomorphic encryption scheme.

Abstract: A method and system for modifying an authenticated and/or encrypted message by a modifying party exchanged between a sending party and a receiving party based on a secure communication protocol, the method includes the steps of a) dividing a clear message into non-modifiable parts and modifiable parts by the sending party; b) including modifiable part information into the message by the sending party; c) authenticating and/or encrypting the message by the sending party; d) providing en- and decryptability and/or authenticability of the message to the modifying party in such a way that the modifying party can only modify the modifiable parts of the message; e) modifying one or more modifiable parts by the modifying party; and f) providing an authenticated and/or encrypted modified message according to the secure communication protocol to the receiving party.

Abstract: A method for providing a public key/secret key pair for encrypting and decrypting data, wherein the public key of the public key/secret key pair and a master secret key are generated based on predefined policy information, and wherein the secret key of the public key/secret key pair is generated based on the generated master secret key and predefined attribute information. A method for accessing a system in an untrusted environment and a system for providing a public key/secret key pair for encrypting and decrypting data as well as a use for access control are also described.