Method for safe maintenance filtering of at least one Input/Output es i,j in at least one state on a flow of m successive incoming messages Es j, each incoming message Es j comprising: - a set of n j of said Inputs/Outputs es i,j (i = 1,...,n j), each of which can be characterised by s i states P q,i,j, each state P q,i,j being associated with a value v q,i,j to which said Input/Output es i,j is equal when it is in said state P q,i,j; - a checksum ∑Sesi,j of signatures Sesi,j, each signature Sesi,j being intended to code said Input/Output esi,j; - and a date dj to date the checksum, said date being incremented by a date increment at each incoming message; said maintenance filtering method being capable of generating from each incoming message Es j an outgoing message Esm j, such that the outgoing message Esm j generated from the incoming message Es j comprises: - a set of n j Inputs/Outputs esm i,j, each of which can be characterised by said s i states P q,i,j, the value v q,i,j of the Input/Output esm i,j of the outgoing message Esm j being able to be equal to or different from the value v q,i,j of the Input/Output es i,j of the incoming message Es j as a function of possible maintenance of the state P q,i,j of the Input/Output es i,j, the value v q,i,j of the Input/Output esm i,j of the outgoing message Esm j being equal to a value vq,i,t of an Input/Output esmi,t of an outgoing message Esmt whatever the state Pq,i,j of the Input/Output esi,j of the incoming message Esj if and only if there exists a tth incoming message Est,j-Ti ≤ t < j, such that the state Pq,i,j of the Input/Output esi,t of the tth incoming message Est is a state intended to be maintained for a period Ti; - a checksum ∑Sesmi,j of signatures Sesmi, each signature Sesmi,j being intended to code the Input/Output esmi,j as a function of the state of the Input/Output esi,j; - and said date dj; the maintenance filtering method according to the invention is characterised in that it comprises: - a calculation of each checksum ΣSesmi,j of the outgoing message Esmj by adding at least one compensation to said checksum ∑Sesi,j, said compensation being calculated as a function of a current state of a pseudo-random generator and an item taken from a compensation table such that the checksum ΣSesmi,j characterising the outgoing message is coherent with the states of the Inputs/Outputs esmi,j of said outgoing message, said item being predefined as a function of a current state of the pseudo-random generator, of the Input/Output esi,j, of the state of the Input/Output es i,j and of the check signature Ses i,j. - a set of n j of said Inputs/Outputs es i,j (i = 1,...,n j), each of which can be characterised by s i states P q,i,j, each state P q,i,j being associated with a value v q,i,j to which said Input/Output es i,j is equal when it is in said state P q,i,j; - a checksum ∑Sesi,j of signatures Sesi,j, each signature Sesi,j being intended to code said Input/Output esi,j; - and a date dj to date the checksum, said date being incremented by a date increment at each incoming message; - a set of n j Inputs/Outputs esm i,j, each of which can be characterised by said s i states P q,i,j, the value v q,i,j of the Input/Output esm i,j of the outgoing message Esm j being able to be equal to or different from the value v q,i,j of the Input/Output es i,j of the incoming message Es j as a function of possible maintenance of the state P q,i,j of the Input/Output es i,j, the value v q,i,j of the Input/Output esm i,j of the outgoing message Esm j being equal to a value vq,i,t of an Input/Output esmi,t of an outgoing message Esmt whatever the state Pq,i,j of the Input/Output esi,j of the incoming message Esj if and only if there exists a tth incoming message Est,j-Ti ≤ t < j, such that the state Pq,i,j of the Input/Output esi,t of the tth incoming message Est is a state intended to be maintained for a period Ti; - a checksum ∑Sesmi,j of signatures Sesmi, each signature Sesmi,j being intended to code the Input/Output esmi,j as a function of the state of the Input/Output esi,j; - and said date dj; - a calculation of each checksum ΣSesmi,j of the outgoing message Esmj by adding at least one compensation to said checksum ∑Sesi,j, said compensation being calculated as a function of a current state of a pseudo-random generator and an item taken from a compensation table such that the checksum ΣSesmi,j characterising the outgoing message is coherent with the states of the Inputs/Outputs esmi,j of said outgoing message, said item being predefined as a function of a current state of the pseudo-random generator, of the Input/Output esi,j, of the state of the Input/Output es i,j and of the check signature Ses i,j.