calculate the average of three encrypted numbers

Question

Is possible to calculate average of three encrypted integer? No constrain on the method of encrypting. The point of this is just to hide the three numbers and find average.

Answer 1

What you seem to be looking for is called Homomorphic Encryption: an encryption scheme which allows you to perform operations on encrypted data, with the encrypted result as the outcome.

Such a scheme would allow you to give encrypted data to a 3rd party, which could then do computations on it for you without knowing what they were computing.

In your case, you need two operations: addition and division. Until recently, homomorphic encryption schemes typically supported only 1 operation. But in september 2009 IMB announced the first fully homomorphic cryptosystem. Other researches published another system soon after that.

These cryptosystems might be be able to do what you want, but it is all cutting edge computer science research.