Abstract: Disclosed is a method (160) for identifying potential tamper in a candidate document having content affected by noise. A candidate content value for each of a plurality of sub-regions of the candidate document and an original content value for each of a plurality of sub-regions of a corresponding original document are determined. The content values are desirably determined based on at least one characteristic of the content in the corresponding sub-region. The candidate content values (330) are associated with the corresponding original content values and a distribution of the candidate content values based on the corresponding original content values is determined. The method characterizes (340) the noise in the candidate document by determining an expected content value range based on the spread of a selected part of the distribution of candidate content values. The method can then identify (350) candidate content values outside the expected content value range as potential tamper.

Abstract: Disclosed is a method (160) for identifying potential tamper in a candidate document having content affected by noise. A candidate content value for each of a plurality of sub-regions of the candidate document and an original content value for each of a plurality of sub-regions of a corresponding original document are determined. The content values are desirably determined based on at least one characteristic of the content in the corresponding sub-region. The candidate content values (330) are associated with the corresponding original content values and a distribution of the candidate content values based on the corresponding original content values is determined. The method characterises (340) the noise in the candidate document by determining an expected content value range based on the spread of a selected part of the distribution of candidate content values. The method can then identify (350) candidate content values outside the expected content value range as potential tamper.