| 摘要 |
A method of encryption, using an encryption key K with key length k, of at least one message M comprising uniformly distributed symbols, k bits are encrypted (830) of messages at least k bits long, while shorter messages are lengthened (840), e.g. by padding or concatenation, to obtain a lengthened message at least k bits long before encryption. The encryption efficiency is thus optimised while the encryption security is retained. The encryption method is particularly suitable for JPEG2000 encoded packets comprising a message M. Also provided are an encryption apparatus (710), a decryption method and a decryption apparatus (910). |
