Verification of authenticity

A system for determining whether an article under test is the same article as a previously tested, the system comprising:

• a signature determination unit operable to determine a signature from an article, the signature determination unit comprising:
• a reading volume for receiving an article;
• a source for generating a coherent beam and directing the coherent beam sequentially onto a plurality of regions of a surface of an article in the reading volume;
• a detector arrangement for collecting a set comprising groups of data points from signals obtained when the coherent beam scatters from an intrinsic structure of the different regions of an article in the reading volume, wherein different ones of the groups of data points relate to scatter from the intrinsic structure of the respective different regions of the article;
• and
• a data acquisition and processing unit for determining a signature of the article from the set of groups of data points;
• and
• a comparison unit operable to determining whether an article under test is the same article as a previously tested article by comparing the determined signature to a stored signature for the previously tested article;
• wherein the comparison unit is operable to split the determined signature into blocks of contiguous data and to perform a comparison operation between each block and respective blocks of the stored signature.