Why does a judge refer to hash value as “hash mark”

It’s not his fault, upon further investigation I found that certain legal writings are lousy with the term.

Here is the paragraph that started me on this investigation:

Defendant's concerns regarding maintaining the integrity of the spreadsheet's values and data could have been addressed by the less intrusive and more efficient use of "hash marks." For example, Defendant could have run the data through a mathematical process to generate a shorter symbolic reference to the original file, called a "hash mark" or "hash value," that is unique to that particular file. 74 This "digital fingerprint" akin to a tamper-evident seal on a software package would have shown if the electronic spreadsheets were altered. When an electronic file is sent with a hash mark, others can read it, but the file cannot be altered without a change also occurring in the hash mark. 75 The producing party can be certain that the file was not altered by running the creator's hash mark algorithm to verify that the original hash mark is generated. 76 This method allows a large amount of data to be self-authenticating with a rather small hash mark, efficiently assuring that the original image has not been manipulated.

Williams v. Sprint/United Mgmt. Co., 230 F.R.D. 640, 655 (D. Kan. 2005)

In Williams v Sprint Judge Waxse cites an article from 1999:

Dean M. Harts, Reel to Real: Should You Believe What You See?, 66 Def. Couns. J. 514, 522 (1999)

B. Use Hash Marks Another option involves running a data or image file through a mathematical process to generate a shorter symbolic reference to the original file, called a "hash mark,"that is unique to that particular file. When the same file is processed through the same algorithm, the same hash mark will result. Anew hash mark necessarily results whenever the base message is altered in any manner. The hash mark is a standard size, usually much smaller than the file, so relatively large files can be verified with the addition of a relatively small amount of data. 66 When a file is sent with a hash mark, others can read it, but the file cannot be altered without a change also occurring in the hash mark. The recipient can be certain that the file was not altered by running the creator's hash mark algorithm to verify that the original hash mark is generated. Thus,the large amount of data involved in digital imaging could be self authenticating with a rather small hash mark,efficiently assuring that the original image has not been manipulated.

Harts’ article was written in 1999. Perhaps the vernacular has changed since then. However, Ralph Losey used “hash mark” in 2007 in his paper Hash: The New Bates Stamp.

Unlike a Bates stamp, a hash mark cannot be added to a native file directly because this would change the file and create an entirely new hash mark. However, you can modify the original name of the file to include the hash mark abbreviation because only the contents of a file are hashed, not the file name. Thus the original name of the computer file could be followed with the hash mark abbreviation; “Bill47.doc” would become “Bill47#A5D.7C1.doc.”

In this example Losey uses the phrase of his own accord but perhaps he got it from one of the two sources he cites:

U.S. District Court for the District of Maryland, Suggested Protocol for Discovery of Electronically Stored Information and Williams v. Sprint/United (same that I quote above).

Because identifying information may not be placed on ESI as easily as bates-stamping paper documents, methods of identifying pages or segments of ESI produced in discovery should be discussed, and, specifically, and without limitation, the following alternatives may be considered by the parties: electronically paginating Native File ESI pursuant to a stipulated agreement that the alteration does not affect admissibility; renaming Native Files using bates-type numbering systems, e.g.,ABC0001, ABC0002, ABC0003, with some method of referring to unnumbered “pages” within each file; using 21 software that produces “hash marks” or “hash values” for each Native File; placing pagination on Static Images; or any other practicable method. The parties are encouraged to discuss the use of a digital notary for producing Native Files

U.S. District Court for the District of Maryland, Suggested Protocol for Discovery of Electronically Stored Information

Then I find a book, written in 2009 that quotes Sprint but does not independently use “hash mark.” Discovery Problems and Their Solutions By Paul W. Grimm, Charles S. Fax, Paul Mark Sandler. Grimm et al also tell us to look at Losey’s paper.

A party’s ESI privilege log will contain different information, depending on which of these approaches that party uses. For ex- ample, if a party renames its Native Files using a bates-type numbering system, the party's ESI privilege log will list each privileged item by its file name. On the other hand, if “hash values” are used to identify ESI materials, each file will be identified by its hash value. A hash value is a “unique numerical identifier that can be assigned to a file, a group of files, or a portion of a file, based on a standard mathematical algorithm[.]" Lorraine v. Markel American Ins. Co., 241 F.RD. 534, 546 (D. Md. 2007) (citation omitted). “‘Hashing’ is used to guarantee the authenticity of an original data set and can be used as a digital equivalent of the Bates stamp used in paper document production." Id. at 546-47. Put another way, a hash value is a “digital fingerprint akin to a tamper-evident seal on a software pack- age. . . . When an electronic file is sent with a hash mark, others can read it, but the file cannot be altered without a change also occurring in the hash mark.” Williams v. Sprint/United Mgmt. Co., 230 F.RD. 640 (D. Kan. 2005); see also Ralph C. Losey, Hash: The New Bares Stamp, 12 J. TECH. L. & POL’Y l (2007). Id.

In Lorraine v. Markel Am. Ins. Co. (PWG-06-1893, at 25-26 (D. Md. May 4, 2007)) Judge Grimm says that “one method of authenticating electronic evidence under Rule 901(b)(4) is the use of ‘hash values’ or ‘hash marks’ when making documents.” Not surprising Judge Grimm cites Williams v Sprint. (He also cites Managing Discovery of Electronic Information: A Pocket Guide for Judges but that guide does not refer to hash marks.)

There are a few books which provide a glossary with the following:

Hash: An algorithm that creates a value to verify duplicate electronic documents. A hash mark serves as a digital thumbprint.

Cyber Forensics: A Field Manual for Collecting, Examining, and Preserving Evidence of Computer Crimes By Albert Marcella, Jr., Doug Menendez

Matthew Bender Practice Guide:  California E-Discovery and Evidence Feb 25, 2015
by Michael F. Kelleher

This definition of hash mark appears to have originated with RenewData’s glossary (in 2005) and was referenced on edrm.net where it got picked up. RenewData later started using this definition:

Hash: an algorithm that creates a value to verify duplicate electronic documents. A hash value serves as a digital thumbprint.

Do you see what they did there?

What are hash marks? Really? # is a hash mark. As in shift + 3 on your keyboard. A hash mark is not the same thing as a hash value.

A New York Times article also refers to hash value as a hash mark but that seems to be an isolated instance.

Designing digital systems that can preserve information for many generations is one of the most vexing engineering challenges. The researchers’ solution is to create a publicly available digital fingerprint, known as a cryptographic hash mark, that will make it possible for anyone to determine that the documents are authentic and have not been tampered with. The concept of a digital hash was pioneered at I.B.M. by Hans Peter Luhn in the early 1950s. The University of Washington researchers are the first to try to simplify the application for nontechnical users and to try to offer a complete system that would preserve information across generations.

A search for “cryptographic hash mark” yields results that are all related to the subject of this NYT article.

In short, “hash mark” is not an appropriate substitution for “hash value” but because a paper written by a law student in 1999 referred to the hash mark the term has become embedded in the vernacular of our times.

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