Method for identifying a physical unit in an open wireless telecommunications network by means of a testing device, having the steps of: a) storing a secret identity (SIMEI) and an open identity (IMEI) in the physical unit, wherein a one-way representation F1 generates the secret identity (SIMEI) from the open identity (IMEI) and a manufacturer key (MIGK), and storing an open key (EMIGK) on an open Internet homepage OMHP belonging to the manufacturer of the device M to be identified, which key is generated from a first secret key (SMMK) of the manufacturer and the second secret key (MIGK, Master Identity Generator Key) by means of a cryptographic function F2; b) generating a first parameter (CHv) in the testing device; c) transmitting an identification request containing the first parameter (CHv) from the testing device to the physical unit; d) generating an electronic signature (SIGt) in the physical unit, by means of a first cryptographic function, from the secret identity (SIMEI), the first parameter (CHv) and a second parameter (CHt) which is generated by the physical unit, wherein the first and second parameters (CHv; CHt) are multiplexed and are then linked to the output (SIGt) of the first cryptographic function by means of an exclusive OR function (+), and transmitting the generated electronic signature (SIGt), the open identity (IMEI) and the second parameter (CHt) to the testing device; e) generating the secret identity (SIMEI) from an open key (EMIGK) downloaded from the open directory of the manufacturer and the received open identity (IMEI) in the testing device, wherein the secret identity (SIMEI) is generated by using the manufacturer key (MIGK) and the open identity (IMEI) via the third function F1, wherein the second secret manufacturer key (MIGK) is generated from the open key (EMIGK) and the first secret manufacturer key (SMMK) by means of the inverse of the second cryptographic function F2 -1; f) generating a corresponding electronic signature (SIGv), by means of the first cryptographic function, from the generated first secret identity (SIMEI), the first parameter (CHv) and the second parameter (CHt) which is received from the physical unit in the testing device, wherein the first and second parameters (CHv; CHt) are multiplexed and are then linked to the output (SIGv) of the first cryptographic function by means of an exclusive OR function (+); and g) identifying the physical unit by comparing the transmitted electronic signature (SIGt) and the generated corresponding electronic signature (SIGv) in the testing device. a) storing a secret identity (SIMEI) and an open identity (IMEI) in the physical unit, wherein a one-way representation F1 generates the secret identity (SIMEI) from the open identity (IMEI) and a manufacturer key (MIGK), and storing an open key (EMIGK) on an open Internet homepage OMHP belonging to the manufacturer of the device M to be identified, which key is generated from a first secret key (SMMK) of the manufacturer and the second secret key (MIGK, Master Identity Generator Key) by means of a cryptographic function F2; b) generating a first parameter (CHv) in the testing device; c) transmitting an identification request containing the first parameter (CHv) from the testing device to the physical unit; d) generating an electronic signature (SIGt) in the physical unit, by means of a first cryptographic function, from the secret identity (SIMEI), the first parameter (CHv) and a second parameter (CHt) which is generated by the physical unit, wherein the first and second parameters (CHv; CHt) are multiplexed and are then linked to the output (SIGt) of the first cryptographic function by means of an exclusive OR function (+), and transmitting the generated electronic signature (SIGt), the open identity (IMEI) and the second parameter (CHt) to the testing device; e) generating the secret identity (SIMEI) from an open key (EMIGK) downloaded from the open directory of the manufacturer and the received open identity (IMEI) in the testing device, wherein the secret identity (SIMEI) is generated by using the manufacturer key (MIGK) and the open identity (IMEI) via the third function F1, wherein the second secret manufacturer key (MIGK) is generated from the open key (EMIGK) and the first secret manufacturer key (SMMK) by means of the inverse of the second cryptographic function F2 -1; f) generating a corresponding electronic signature (SIGv), by means of the first cryptographic function, from the generated first secret identity (SIMEI), the first parameter (CHv) and the second parameter (CHt) which is received from the physical unit in the testing device, wherein the first and second parameters (CHv; CHt) are multiplexed and are then linked to the output (SIGv) of the first cryptographic function by means of an exclusive OR function (+); and g) identifying the physical unit by comparing the transmitted electronic signature (SIGt) and the generated corresponding electronic signature (SIGv) in the testing device.