GROUP ENCRYPTION METHODS AND DEVICES

摘要

The present invention improves on prior art group encryption schemes by encrypting an alias of a recipient's public key instead of the public key itself. A Group Manager publishes the encryption of the alias,the corresponding public key and a corresponding certificate on a public database DB. The alias is a resulting value of a suitably chosen function ƒ on the public key, and can be viewed as a hash of the public key. This can allow a significant decrease in the size and cost of the resulting construction as the alias can be made smaller than the public key. In particular, there is no need to apply the second encryption scheme as many times as there are group dements in the recipient's public key.

主权项

1. A method of group encrypting a plaintext m with regard to a tag t for a recipient with a public key pk to obtain a ciphertext the method comprising at a device:
creating a first encrypted value c1 and a second encrypted value c2, by calculating c1=E1.Encrypt{pk}(m,OTS.vk) and c2=E2.Encrypt{pkOA} (f(pk),OTS.vk), wherein E1 is a first encryption algorithm, E2 is a second encryption algorithm, pkOA is a further public key, OTS.sk is a signing key, OTS.vk is a verifying key and ƒ is a mapping function; producing a signature s on the first encrypted value c1, the second encrypted value c2 and the tag t using the signing key OTS.sk by calculating s=OTS.Sign{OTS.sk}(c1,c2,t), wherein OTS.Sign is a signature algorithm; and outputting the ciphertext c, wherein the ciphertext c comprises the first encrypted value c1, the second encrypted value c2, the verifying key OTS.vk and the signature s.