1. A method of securely computing a measure of similarity for at least two sets of data, the method comprising: obtaining a first set of encrypted data and a first set of plaintext data; encrypting the first set of plaintext data, wherein a second set of encrypted data is created; computing, based on in part the first set of encrypted data and in part the second set of encrypted data, a measure of similarity for said first and second set of encrypted data; providing a publicly verifiable proof that the encrypted sets of data and the measure of similarity have been correctly computed; determining whether the measure of similarity complies with a predetermined criteria; wherein the data employed is extracted from a biometric feature of an individual, and the encryption performed comprises homomorphic encryption.