A method for a secure transmission of information between a first and a second module is disclosed. Each module contains one of the keys of two pairs of keys. A first number and a second number are randomly generated in the first module, and a third number is randomly generated in the second module. A check is made that a random number encrypted by one of the modules, then decrypted by the other, then re-transmitted re-encrypted to the initial module, is after decryption in the latter identical to the original random number. In each of the modules a common session key K is created independently with at least three same numbers generated randomly partially in one module and partially in the other module. Information transmitted between the two modules is encrypted with the common session key.