Method of execution of a binary code of a secure function by a microprocessor

Method of execution of a binary code of a secure function by a microprocessor, wherein this method comprises:

• a) the provision of the binary code, this binary code comprising code lines, each code line containing:
• a cryptogram of a single instruction executable by the microprocessor or of a single datum to be processed by the microprocessor, and
• a message authentication code making it possible to verify the integrity and the authenticity of the cryptogram,
• b) during the execution of the binary code by the microprocessor, each time the microprocessor loads a code line, the method comprises the following operations:
• 1) a securing hardware module of the microprocessor verifies the integrity and the authenticity of the cryptogram contained in the code line loaded with the aid of the message authentication code contained in this same line and triggers the signalling of an execution fault if the integrity or the authenticity of the cryptogram is not confirmed, and then
• 2) the securing hardware module decrypts the cryptogram to obtain a decrypted instruction or a decrypted datum if the integrity and the authenticity of the cryptogram are confirmed, and then:
• in the case of a decrypted instruction, the decrypted instruction is recorded in a queue of instructions to be executed successively one after another by an arithmetic and logic unit of the microprocessor, and
• in the case of a decrypted datum, the decrypted datum is recorded in an internal register of the microprocessor while waiting to be processed by the arithmetic and logic unit, and in which:
• during step a), the cryptogram contained in the code line is a cryptogram of a concatenation:
• of the said instruction or datum, and
• of a first error-detecting code making it possible to detect an error in the instruction or in the datum with which it is concatenated,
• during the operation, the decryption of the cryptogram by the securing hardware module makes it possible to obtain, in addition to the decrypted instruction or to the decrypted datum, the first decrypted error-detecting code, and then:
• in the case of a decrypted instruction, the first decrypted error code is recorded in the queue of instructions with the decrypted instruction, and
• in the case of a decrypted datum, the decrypted datum and the first decrypted error-detecting code are recorded in one and the same register of the microprocessor, and
• after the operation 2), the method comprises the following operation 3):
• when the next instruction to be executed contained in the queue of instructions is the instruction decrypted during the operation 2), the securing hardware module verifies, with the aid of the first error-detecting code recorded with this decrypted instruction, whether there exists an error in this decrypted instruction, and, in the case where such an error is detected in this decrypted instruction, the securing hardware module triggers the signalling of an execution fault, and, in the case where no error has been detected in this decrypted instruction, the microprocessor decodes the decrypted instruction and transmits it to the arithmetic and logic unit which executes it, or
• when the next datum to be processed by the arithmetic and logic unit is the datum decrypted during the operation 2), the securing hardware module verifies with the aid of the first error-detecting code recorded associated with this decrypted datum, whether there exists an error in this decrypted datum, and, in the case where such an error is detected, the securing hardware module triggers the signalling of an execution fault, and, in the case where no error is detected, the arithmetic and logic unit processes this decrypted datum.