INSTANCE HANDLING OF A TRUSTED EXECUTION ENVIRONMENT

There is provided mechanisms for handling instances of a trusted execution environment on an execution platform. The trusted execution environment is associated with a secure cryptoprocessor. The secure cryptoprocessor holds a register. The trusted execution environment is configured to read from and write to the register at a given index i. A method is performed by the trusted execution environment. The method comprises checking, upon start of a new instance of the trusted execution environment, status of the register at the given index i, and wherein, when the register at the given index i has its status set to "undefined", an internal status value is set to a first value, and else, when a value is read from the register at the given index i, the internal status value is set to a second value based on the read value. The method comprises writing the internal status value to the register at the given index i. The method comprises running the new instance. The method comprises, whilst running the new instance, reading a current value from the register at the given index i. The method comprises enabling the new instance to keep running only when the current value equals the internal status value.