Some weak points of one fast cryptographic checksum algorithm and its improvement

In this paper, we examine a previously published fast cryptographic checksum algorithm used for maintaining the integrity of files in an information system. We find two flaws in the previous analysis: it is possible to append information to a file and generate a new valid cryptographic checksum for the modified file, and it is possible to forge changes to blocks whose value is less than the modulus used in the scheme under examination. We then show how this method can be improved to eliminate these problems while still maintaining its other beneficial properties.