A method for securing a white box cryptographic function computation on cryptographic device such that a cryptography key K, used to encrypt a plaintext into a ciphertext, is not used in a plaintext form, comprising: receiving a first message ( PK HE 511 or m 1303); receiving a message ( EK HE) containing a cryptography key encrypted using the first homomorphic encryption key ( EK HE) using a homomorphic encryption scheme; performing a cryptographic operation on the first message (511 or 1303) using the encrypted cryptography key ( EK HE 509) thereby producing a cryptography function output ( EK HE 517 or EK HE 1309)) encrypted using the first homomorphic encryption key ( EK HE); associating each step j of each computation block i of the cryptographic operation with a verification value ( ea ij, a ij) and verification sum ( A, EA) wherein one of the verification sum is an encryption of the sum of the verification values ( a ij) or the verification sum is the sum of plaintext values ( a ij) corresponding to the verification values ( ea ij); using homomorphic encryption, encrypting one of the verification value and the verification sum and not encrypting the other of the verification value and the verification sum; and for each step j of each round i of the cryptographic function assigning a tracer value ( t ij,et ij) with the verification value corresponding to that step i,j; at the conclusion of the cryptographic function, calculating a tracer sum ( eT, T) of all the tracer values; performing one of the calculation of sum of tracer values or the sum of verification values on encrypted values ( et, ea) and performing the other of the calculation of the sum of tracer values or the sum of verification values on plaintext values ( t, a); and comparing the calculated tracer sum ( T, ET) with the expected verification sum ( A, EA). receiving a first message ( PK HE 511 or m 1303); receiving a message ( EK HE) containing a cryptography key encrypted using the first homomorphic encryption key ( EK HE) using a homomorphic encryption scheme; performing a cryptographic operation on the first message (511 or 1303) using the encrypted cryptography key ( EK HE 509) thereby producing a cryptography function output ( EK HE 517 or EK HE 1309)) encrypted using the first homomorphic encryption key ( EK HE); associating each step j of each computation block i of the cryptographic operation with a verification value ( ea ij, a ij) and verification sum ( A, EA) wherein one of the verification sum is an encryption of the sum of the verification values ( a ij) or the verification sum is the sum of plaintext values ( a ij) corresponding to the verification values ( ea ij); using homomorphic encryption, encrypting one of the verification value and the verification sum and not encrypting the other of the verification value and the verification sum; and for each step j of each round i of the cryptographic function assigning a tracer value ( t ij,et ij) with the verification value corresponding to that step i,j; at the conclusion of the cryptographic function, calculating a tracer sum ( eT, T) of all the tracer values; performing one of the calculation of sum of tracer values or the sum of verification values on encrypted values ( et, ea) and performing the other of the calculation of the sum of tracer values or the sum of verification values on plaintext values ( t, a); and comparing the calculated tracer sum ( T, ET) with the expected verification sum ( A, EA).