A coupling and chaining bridge configured to: - operate a coupling between a random access memory coupled to the coupling and chaining bridge via a first bus and a cryptographic circuit , coupled to the coupling and chaining bridge via a second bus , in response to a write access request for data into the random access memory, wherein the write access request comes from a processor coupled to the coupling and chaining bridge via a system bus and a third bus , wherein the access request further comprises an address for storing into the random access memory, the coupling operation comprising: writing the data into the random access memory; the coupling and chaining circuit being characterized in that the coupling operation further comprises: for each piece of data, generating a first write access request into the cryptographic circuit for the piece of data, and generating a second write access request into the cryptographic circuit, for the storage address; - operate a checking, between the cryptographic circuit and the random access memory in response to a read access request from the processor, of a verification value stored in the cryptographic circuit, the checking operation comprising: the comparison of the verification value with a reference value that is stored in an internal register of the coupling and chaining bridge; and - based on the comparison, give access to the random access memory in read-only mode. - operate a coupling between a random access memory coupled to the coupling and chaining bridge via a first bus and a cryptographic circuit , coupled to the coupling and chaining bridge via a second bus , in response to a write access request for data into the random access memory, wherein the write access request comes from a processor coupled to the coupling and chaining bridge via a system bus and a third bus , wherein the access request further comprises an address for storing into the random access memory, the coupling operation comprising: writing the data into the random access memory; the coupling and chaining circuit being characterized in that the coupling operation further comprises: for each piece of data, generating a first write access request into the cryptographic circuit for the piece of data, and generating a second write access request into the cryptographic circuit, for the storage address; writing the data into the random access memory; the coupling and chaining circuit being characterized in that the coupling operation further comprises: for each piece of data, generating a first write access request into the cryptographic circuit for the piece of data, and generating a second write access request into the cryptographic circuit, for the storage address; - operate a checking, between the cryptographic circuit and the random access memory in response to a read access request from the processor, of a verification value stored in the cryptographic circuit, the checking operation comprising: the comparison of the verification value with a reference value that is stored in an internal register of the coupling and chaining bridge; and - based on the comparison, give access to the random access memory in read-only mode. <EOS>