Practical Windows Forensics

Evidence integrity (the hash function)

What can we do to prove that the evidence hasn't been altered or changed? This step is very important to prove in court, if required, that you didn't add, remove, or edit the evidence during imaging or analysis. Most of the imaging tools come with many hash function implementations, such as MD5, SHA1, and SHA256. The hash function is a mathematical implementation, which is an irreversible or one-way function. This means that if you have input data A and hash function F, you will get F(A) = H. However, it's been proved that F'(H) != A, where F is the hash function and F' is any mathematical function. We can't get A, the original data, from H, the hash digest.

For example, if we have different strings applied ...