Bullet signature measurement with chromatic confocal sensor.

A new, non-contact, three-dimensional (3D) bullet signature measuring system based on a chromatic confocal sensor is developed. The system is composed of a precision rotary table and a chromatic confocal sensor. The measurement uncertainty of the system is less than 1 µm. When measuring the surface topography of the object, the sensor acquires wavelength information reflected from the object instead of intensity information. This advantage is very suitable to bullet signature measurements. The chromatic confocal sensor works in the point measuring mode and can acquire data continuously with high speed. One round section measurement on the bullet body takes less than 1 minute.

Asymmetric cryptography based on wavefront sensing.

A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

Chosen-plaintext attack on lensless double-random phase encoding in the Fresnel domain.

We demonstrate a method of chosen-plaintext attack on lensless double-random phase encoding (L-DRPE) in the Fresnel domain. With this attack an opponent can access two encryption keys with help of the impulse functions as chosen plaintexts. This shows that a lensless optical encryption scheme based on DRPE is vulnerable to chosen-plaintext attack. Cryptoanalysis also indicates that the security worry originates from the linearity of the encryption and decryption mechanism of the L-DRPE scheme. One of the interesting features of the proposed attack is that the decryption process is lossless. Numerical simulations show good agreement with theoretical analysis.

Known-plaintext attack on optical encryption based on double random phase keys.

We demonstrate a new approach to known-plaintext attack on an optical encryption scheme based on double random phase keys. With this attack an opponent can access both random phase keys with the help of the phase retrieval technique. This demonstration shows that an optical encryption scheme based on double random encoding is vulnerable to known-plaintext attack.