In some of these spy movie and action movies you see "the mark" get their keys picked, imprinted and cut (duplicated) by the master spy or even ultimate criminal. The "echo my key" aims to make this extremely difficult to do to near impossible.
The premise of the key is to design defects into the key that can be identified using NDT (non destructive testing) methods such as ultrasonic detection. As illustrated in the attached images, the various defects integrated into the key mean that cutting the key would not give you a duplicate key for it will not be identical internally.
As the unique key is inserted into the lock, ultrasonic transducers would probe and record feedback of the internal defects back to an integrated computer to verify if that key is authorised to open the lock or grant access.
Concerns that the key can be scanned and later duplicated can be alleviated by manufacturing the defects from various materials that give different responses.
This has application both in the commercial market and defence security market, for example in bank or home safes and high security facilities entrances where security is paramount.
With integrated ultrasonic and computer systems/programmes already available in the market at large (equipment used in automotive and aerospace manufacturing), the biggest challenge will be designing the key.
The external components of the key can be made of various materials, but for durability proposals would be to use a metal like stainless steel. This can be cast or machined with the designer either opting to create two halves to be later welded together or casting the whole key as illustrated in image. This manufacturing techniques are not exhausted as techniques such as 3D printing is also viable.