Space-efficient, byte-wise incremental and perfectly private encryption schemes

The problem raised by incremental encryption is the overhead due to the larger storage space required by the provision of random blocks together with the ciphered versions of a given document. Besides, permitting variable-length modifications on the ciphertext leads to privacy preservation issues. In this paper we present incremental encryption schemes which are space-efficient, byte-wise incremental and which preserve perfect privacy in the sense that they hide the fact that an update operation has been performed on a ciphered document. For each scheme, the run time of updates performed turns out to be very efficient and we discuss the statistically adjustable trade-off between computational cost and storage space required by the produced ciphertexts

Efficient authentication of large, dynamic data sets using Galois/Counter Mode (GCM)

The Galois/Counter Mode (GCM) of operation can be used as an incremental message authentication code (MAC); in this respect, it is unique among the crypto algorithms used in practice. We show that it has this property, and show how to use it as an incremental MAC. These MACs have great utility for protecting data at rest. In particular, they can be used to protect a large, dynamic data set using only a small, constant amount of memory