Homomorphic encryption is an old idea but only in 2009 and the work of Gentry started to have some possible practical applications. Since then there have been quite impressive improvements in the research in this field of cryptography, also due to the need to improve the security of data managed by Cloud systems.
In brief, homomorphic algorithms are cryptographic algorithms that allow to do computations, like sums, multiplications, searches etc., on encrypted data giving encrypted results, without knowing the encryption key.
It should be obvious that these algorithms would be very useful for Clouds’ applications since the owner of the data would be able to use the data remotely by keeping at the same time the data, and the result of the computations, always encrypted in the Cloud application.
Unfortunately homomorphic encryption is not ready yet for general use, but it has just appeared an interesting research paper by Microsoft Reasearch announcing the release of a SEAL (Simple Encryption Arithmetic Library), a library for using homomorphic encryption in bioinformatics, genomic and other research areas.