Canadian Lawyer

w w w . C A N A D I A N L a w y e r m a g . c o m M A r C h 2 0 1 5 19 on briefs; Bates numbers; or production numbers. Hash values rarely serve as pri- mary control numbers, but often as sec- ondary or cross-reference control numbers. When productions are exchanged, particu- larly if native files are produced, parties may request that record's hash value accompany the production as a metadata field. In this way, the hash value serves both to identify the record (so that the receiving party can use it as a document reference number) but can also be used to compare and iden- tify duplicates in documents from different sources. The use of hash values as evidence con- trol numbers has at least two problems: one relates to the security of the hash value; the other to limited uncertainty around how hash values are generated. The use of hashing as a primary control number has generated controversy among some members of the e-discovery com- munity because there can be collisions of control numbers; particularly when com- paring hash values from different sets, it can be difficult to determine whether the item is a duplicate, is a calculation mishap, or collision. This problem is compounded when the two same hash values have come from different data sources. The only way to deal with a collision in this context is to do an exact comparison on the original data, but in litigation this will generally not be possible. One way around this is to use a more complex hashing function (i.e. SHA-256 or SHA-512), which generate longer "fin- gerprints" that reduce the likelihood of a collision. The other solution is to generate two hash values for each item from separate algorithms since different algorithms will not generate the same collision. Both of these approaches are impractical, as most e-discovery applications do not have this functionality. Even if one accepts that collisions are unlikely, such that one calculation from an MD5 or SHA-1 is acceptable, a second challenge arises from how hash values are calculated in most e-discovery processes. Generally, hashing is done over both the text of a document and a portion of its metadata; however, there is no uniform standard for calculating hashes from meta- data. Therefore, if different metadata is used when hashing the document two times it may be possible to generate two different hash values. Consequently, one party may not be able to use the other party's hash values for deduplication if both parties have used the same algorithm but not calculated hash values the same way. Although there remain technical issues associated with the use of hash values as primary control numbers (to uniquely identify documents for the record), I gen- erally prefer to receive a field containing hash values for secondary control purposes. Obtaining hash values is even more helpful when I can get information from opposing parties about how the hashes were calcu- lated (which algorithm and which source). One hopes that one day the use of hashing in e-discovery will be standardized. Dera J. Nevin is the director of e-discovery services at Proskauer Rose LLP. The opin- ions in this article are entirely her own. The author wishes to thank Eric Robi of Elluma Discovery for his assistance in reviewing this article. Family Law Litigation Handbook – Alberta Edition provides you with practical insight and expert guidance into family law litigation procedures in Alberta that you can access on the spot. You'll always want to keep this essential practice companion within easy reach, to help you think quickly on your feet during court proceedings and client meetings. This new publication offers: • Authoritative insight into family law litigation procedures in Alberta • Practice-based commentary by two leading practitioners • Region-specific court information and particulars • Convenient Child Support Guidelines' table amounts for Alberta • A reference guide to the Spousal Support Advisory Guidelines The second title in the Family Law Litigation Handbook series, Family Law Litigation Handbook – Alberta Edition delivers indispensable content in a concise manner, as the first Family Law Litigation Handbook has for many Ontario family lawyers. New Publication Family Law Litigation Handbook – Alberta Edition Ronald S. Foster, Q.C. and Gary S. Joseph The briefcase staple for quick answers to Alberta family law matters Available risk-free for 30 days Order online: www.carswell.com Call Toll-Free: 1-800-387-5164 In Toronto: 416-609-3800 Order # 986368-65203 $109 Softcover approx. 320 pages August 2014 978-0-7798-6368-6 Shipping and handling are extra. Price(s) subject to change without notice and subject to applicable taxes. 00222UW-A44745

• Cover