Steele's attorney's have made a big stink over the fact that the original recordings were destroyed. They are stuck in the 20th century. All copies of digital recordings are properly considered original.
A hash function is somewhat like a check sum. All the bits of the recording are entered into a complex mathematical function. In this case that function is used to produce a 32 byte string of digits called a hash. This same function can be used on a copy of that recording to see if it is still exactly the same as the original.
Here is an explanation of the details of the recorder by an FBI examiner. The original link is a photo type pdf file and I retyped it.
UNITED STATES DISTRICT COURT
FOR THE DISTRICT OF IDAHO
Criminal Case No. 10-CR-148-BLW
UNITED STATES OF AMERICA,
Affadavit of David J. Snyder III
I, David J. Snyder, III, being duly sworn, depose and say as follows, based on information and belief, the source of which is my training and experience with the FBI in the Forensic Audio, Video and Image Analysis Unit as a Forensic Audio Examiner for 11 years. I have been admitted as an expert in the disciplines of audio enhancement, analog and digital authenticity in Federal, State and Local courts on several occasions. I have a BS degree in Electronics Engineering Technology and an AS in Electrical Engineeering Technology.
1.Duplicate copies of the recordings listed as 1D1 (6/9/10) and 1D2 (6/10/10) by the Federal Bureau of Investigation were provided to the defense in the proprietary format with a version of the proprietary player.
2.The files on 1D1 (6/9/10) and 1D2 (6/10/10) also have "hash values", which are obtained by using a mathematical algorithm to produce a 32-character string value, similar to a finger print, which uniquely indentifies the original data. By comparing the original file's hash value against the hash value of any purported coped of the original file, an examiner can quickly confirm whether the copy is a true, complete and accurate copy of the original. The reliability of hash values is well-established with the computer software, computer forensic examiner, audio forensic examiner and video forensic examiner fields. The hash values of the orginal file matched the copies provided to the defense.
3.The audio recorder used to produce the recordings referenced above was a Flex8F audio recorder.
4.Audio recorded on the Flex8F recorder cannot be monitored or reviewed until it is transferred from the recorder to a computer workstation. A recorder can be connected to a computer workstation to view the session log, but the audio cannot be monitored or reviewed as a feature to protect against tampering. If the recordings are not transferred additional recordings can be added to the recorder.
5.Once recordings are transferred to the computer workstation, the recorder must be erased before new recordings can be produced, also as a hardware protection against tampering.
6.Files transferred from the recorder can be written directly to write-once media, such as a CD-R or DVD-R, as an additonal protection against tampering.
I declare under penalty of perjury that the foregoing is correct on this 15th day of September, 2011.
David J. Snyder III