A privacy-preserving method for performing a disease susceptibility test on a patient, said method comprising: (I) performing homomorphic computations, (J) obtaining a test result which is partly decrypted with a first part (prk1 resp. prk2) of a private key, (L) decrypting said partly decrypted result with a second part (prk2 resp. prk1) of said private key, wherein said homomorphic computations are based on encrypted genomic markers of the patient, on encrypted clinical and/or environmental markers, and on encrypted ancestry markers of the patient. The invention is also related to a method for inferring ancestry in the encrypted domain.