MD5 Checksum Utility The goal of this paper is to define and explore the MD5 checksum utility. It is also my goal to discuss how to use MD5 checksums to support Incident Response. First off, I will start with talking a little about MD5 and where it stems from. In relation to cryptography, MD5 stands for Message Digest Algorithm 5. It is also known as RFC 1321. Cryptography is the basis for secure communications .It is by definition, a science of writing or reading coded message. MD5 falls under the category of Hash Functions. A hash function takes a message of arbitrary length and spits out a fixed length code. The output is called the message digest or hash. One way hash functions are used to provide a "fingerprint" of a message or file. The hash fingerprint is supposed to be unique and because of this can prove the authenticity of the message. MD5 was developed by a professor named Ronald Rivest of the prestigious MIT. He created the algorithm to replace an earlier hash function which was MD4. The main job of this digest is to provide some sort of assurance that a transferred file has indeed arrived intact. MD5 along with another hash function called SHA (Secure Hash Algorithm), are the most widely used in current product implementations. The main MD5 message digest is represented as 16-byte (128-bits) Hexadecimal number ( written as 32 characters using the digits 0-9 and A-F or a-f ). This value can be found all over the internet. The checksum is a type of redundancy check that will verify the data in a number of ways. MD5 allows a string of unique letters and numbers to stand for data. MD5 can be used across all platforms making it universal. You can use it with windows, or any other operating system that you wish. I myself used it on Windows XP and it worked flawlessly. While MD5 checksums are used mostly for data verification and for passwords, it is important to note that applications that decompile MD5 sums are widely available on the internet among other places. One should use caution when storing a password with it.