Two of the more common cryptographic hashing algorithms used are MD 5 and SHA 1. MD 5 provides 128-bit hash value, and an SHA 1 will give a 160-bit hash value, either of these values can be considered a digital fingerprint for a specific file.
If anyone changes a single bit on the source file, it will cause a different hash value to be created. This function makes it very easy to determine if something had changed in the file since the investigator recovered it.