Transferring Video

Keeping Files Intact (and Proving It)

It is important to make sure your files stay intact and unaltered when you transfer. It can also be important to show that your files are intact and unaltered, especially if you are using video for evidence.

MD5 and SHA1 Hash examples.

Hashes, also known as checksums, are a way to check if your files have transferred intact. Hashes are also valuable metadata for evidentiary video, because they can be used to show whether your files are tampered with over time. It is therefore a good idea to capture hashes as early as possible in the video lifecycle, such as when you first offload videos from your camera.

A hash is an alphanumeric string of characters that is created by running a hash function algorithm (such as MD5 or SHA-1) on a file. The resulting hash value will be the same every time you run the algorithm on the file, so long as the file is unchanged. If the file is altered in any way, the resulting hash value will be different.

Run a hash algorithm on a file as soon as you acquire it, and again whenever you want to check that it is intact. You may want to check a file, for example, after you have transferred it from one location to another, if your file has been stored for a long time, or if you want to know whether someone has altered it.

There are many free and commercially available software applications you can use to compute hashes (see “Try This” below). In the near future, some cameras will allow you to compute and embed hashes in the video file at the point of creation.

Karen’s Hasher is a free Windows application for computing hashes.

Karen’s Hasher is a free Windows application for computing hashes.


There is a built-in MD5 tool for Macs. To use this MD5 tool, open a Terminal window, type 'md5,' followed by a space, and then the file (with filepath) you want to hash. Type 'man md5' for the full MD5 tool manual.

There is a built-in MD5 tool for Macs. To use this MD5 tool, open a Terminal window, type ‘md5,’ followed by a space, and then the file (with filepath) you want to hash. Type ‘man md5’ for the full MD5 tool manual.

Try This: BASIC

Karen’s Hasher is a Windows GUI tool for computing and verifying hashes.

Try This: ADVANCED

MD5 is a command-line tool for computing MD5 checksums that comes pre-installed on Macs.

Try This: ADVANCED

Microsoft File Checksum Integrity Verifier is a Windows command-line tool for computing MD5 and SHA1 hashes.

Try This: ADVANCED

md5deep and hashdeep are command-line tools for computing and comparing multiple checksums for entire directories of files.

Try This: ADVANCED

sha1sum is a command-line tool for computing and checking SHA-1 checksums that is part of the GNU Core Utilities.

<< Uploading and Downloading Video

Physical Transport>>

In This Section
  1. Introduction
  2. Offloading from Cameras
  3. Uploading and Downloading Video
  4. Keeping Files Intact (and Proving It)
  5. Physical Transport
  6. Transferring Videos and Metadata Together
Takeaways
  • When offloading videos from your camera to your computer, make sure you transfer the files completely and without alteration.
  • Always make sure to include your metadata and documentation with your video—or make sure they can be matched together after transfer.
  • If using the Internet to transfer files, choose a file sharing service that meets your needs for permanence, data integrity, security, chain of custody, documentation, accessibility, efficiency, and cost.
  • Use hashes to check that your files have transferred intact, and to show that your files have not been altered over time.
  • If physically transporting drives, make sure to have another copy and be aware of cross-platform constraints.
  • Organize your videos in “information packages,” or folders with your video and metadata, for transfer.
The Archiving Workflow

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