A method for providing encrypted data on a client, a cloud or the like includes, providing, for each user, a user-specific encryption key for encrypting user-specific plaintext. A common decryption key is computed with a pre-determined f netion using the user-specific encryption keys as input for the function, The function is a polysized function supporting poly-many additions and a single multiplication. Each user-specific plaintext is encrypted with the corresponding user-specific encryption key resulting in user-specific ciphertexts, The encrypting is performed such that encryption is homomorphic in the user-specific plaintext as well in the user-specific encryption keys. A. common ciphertext is computed with the function using the user-specific ciphertexts as input for the function. The common ciphertext and the common decryption key are provided for decryption.