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 ({ C } PK HE 511 or m 1303); receiving a message ({ K } EK HE ) containing a cryptography key ( K ) 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 ({ K } EK HE 509) thereby producing a cryptography function output ({ M } EK HE 517 or { S } 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 ( EA ) is an encryption of the sum of the verification values ( a ij ) or the verification sum ( A ) 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 ( T ) or the sum of verification values (A) 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 ({ C } PK HE 511 or m 1303); receiving a message ({ K } EK HE ) containing a cryptography key ( K ) 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 ({ K } EK HE 509) thereby producing a cryptography function output ({ M } EK HE 517 or { S } 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 ( EA ) is an encryption of the sum of the verification values ( a ij ) or the verification sum ( A ) 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 ( T ) or the sum of verification values (A) 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 ). <EOS>