Charles wants to ensure that the forensic work that he is doing cannot be repudiated. How can he validate his attestations and documentation to ensure nonrepudiation?

The most important action Charles can take while working with his forensic artifacts to provide nonrepudiation is to digitally sign the artifacts and information that he is creating in his evidence records. Encrypting the output will ensure its confidentiality but will not provide nonrepudiation by itself. MD5 checksums for images are commonly gathered but must then be signed so that they can be validated to ensure they have not been modified.