Process for protection decryption of programmable logic configuration files and circuit implementing the PROCESS

The invention relates to a method for protecting a programmable logic circuit (100, 200) characterized in that the one or more data files used for configuring programmable resources of the circuit are stored in a nonvolatile memory (107 , 207) after summers encrypted (112), an inner decryption module to the circuit (103, 203) being in charge to decrypt the file using a secret key (102, 202) stored in the circuit, the module decryption being protected against attacks to get the key for the decryption operation by implementing at least one technique against measure. The invention also relates to programmable logic circuit of FPGA object protected against attacks by observation and / or fault injection during the decryption operation using the method according to one of the preceding claims.