> Experts are not much closer to solving the problem [of user-friendly cryptography] today than they were two decades ago. I disagree. Recently there have bee

> Experts are not much closer to solving the problem [of user-friendly cryptography] today than they were two decades ago. I disagree. Recently there have been breakthroughs in homomorphic encryption. From Wikipedia [1]: "...any circuit can be homomorphically evaluated, effectively allowing the construction of programs which may be run on encryptions of their inputs to produce an encryption of their output. Since such a program never decrypts its input, it can be run by an untrusted party without revealing its inputs and internal state." While currently known constructions with the right mathematical properties are kind of slow, I'm sure that a lot of people are now interested and in the future we'll eventually be able to do it at practical speeds (especially with the help of future computers that are faster, and/or have more cores, and/or have dedicated coprocessors hard-wired for homomorphic encryption computations, like recent x86 chips have hardware accelerated AES [2]). If this happens, websites will be able to implement features, like search, that rely on manipulation of user data, without having access to that data themselves. > [Certain] features depend on Facebook’s servers having access to a person’s private data Today this is true, at least for people who aren't on the cutting edge of research in this field. But it might not be true tomorrow, if homomorphic encryption ever becomes practical (both in terms of fast algorithms, and in terms of frameworks/libraries which make it easy for developers to use). Off-topic remark: Homomorphic encryption will also impact the economics of cloud computing, since you'll be able to use CPU cycles provided by others without the security concerns of disclosing the unencrypted confidential data you want them to manipulate. [1] http://en.wikipedia.org/wiki/Homomorphic_encryption#Fully_homomorphic_encryption http://en.wikipedia.org/wiki/Homomorphic_encryption#Fully_ho... [2] http://en.wikipedia.org/wiki/AES_instruction_set http://en.wikipedia.org/wiki/AES_instruction_set