The Secret to Good Lawyering Lies in 19th Century Cryptology

Lawyers are good at keeping secrets. Secrecy is written into our code of conduct, incorporated into our rules, and enshrined in the highest pillars of legal culture. Confidentiality is arguably the closest thing to the Hippocratic Oath—the legal profession’s analog to “do no harm.”

Ironically, a lawyer’s duty of secrecy is almost always accompanied with a concomitant duty to disclose. Transactional lawyers are required to provide fulsome disclosures as part of diligence, while litigators are required to disclose their legal theories and produce troves of evidence as part of discovery. While secrecy and disclosure can coexist, there is an inherent tension between the two. After all, the more one discloses, the less one keeps secret, and the more ammunition one provides to the opponent. Striking the correct balance isn’t easy and frequently lands reticent lawyers in hot water.

Law is not the only profession that must navigate this tension. In fact, there is an entire field of study dedicated to maintaining secrecy in the face of mandatory disclosures—cryptology. The quintessential problem in cryptology involves a scenario where two people (typically referred to as “Alice” and “Bob”) must communicate in front of a hostile observer.

Cryptologists seek to devise a system in which Alice can transform her message such that it can be reconstructed by Bob, but not by a third-party observer. While the specifics differ from litigation, both law and cryptology seek to maintain secrecy while providing disclosures to an adversary.

Cryptologists have devised a series of tools to navigate the tension between public and private information. One of the guiding ideas for modern cryptology is Kerckhoff’s Principle, which states that the quality of a crypto-system should turn on the mathematical strength of the system rather than on its secrecy. In other words, “design your system assuming that your opponents know it in detail” means that secrecy is no substitute for quality.

As an example, consider the classic “Caesar-Cipher” system. Under this system, you choose a key number (N) and encode your message by shifting each letter forward in the alphabet by N letters. If you wanted to send HELLO and used a key of 1, your message would be IFMMP. Kerckhoff’s Principle states that the quality of this system depends on how easy it is to recover a message without the key, assuming you know how the system works. Based on this principle, the code is of poor quality, since it would take at most 25 attempts for an adversary to recover any message. Under Kerckhoff’s Principle, the fact that your adversary may not know that you used a Caesar-Cipher doesn’t improve the quality of the encryption scheme, since you designed your system assuming the adversary has complete information.

It turns out that Kerckhoff’s Principle has a direct application to legal proceedings; instead of evaluating encryption schemes and ciphers, we’re evaluating arguments, positions, and legal strategies. In other words, Kerckhoff’s Legal Principle holds that, when assessing an argument (or position, or strategy), lawyers should assume their opponent has full knowledge of the argument and will have sufficient time to identify and exploit its weaknesses. The fact that an argument could win the day by catching an opponent off-guard doesn’t mean the argument is good.

In a sense, KLP is already built into the fabric of the legal system. After all, the rules of civil procedure require robust disclosures and penalize parties who fail to comply. The disclosure requirements, however, aren’t comprehensive and don’t reach every aspect of a case. For example, parties aren’t required to disclose trial themes, settlement strategies, or deposition outlines. Further, the required disclosures are difficult to police, frequently litigated, and often vague and unhelpful.

The point isn’t that parties should disclose more (though, frequently, they should). Instead, the lesson from KLP is that, regardless of formal disclosure requirements, parties shouldn’t rely on secrecy or ambush as a legal strategy but should instead prioritize positions and strategies that can withstand an opponent’s (and the judge’s) scrutiny.

The obvious benefit of adopting KLP is that your arguments will be stronger since KLP requires you to think through and resolve the most persuasive rebuttals and the most threatening counter-strategies. KLP is also beneficial since it means arguments will be robust to unexpected events that negate any “surprise” advantage.

For example, consider a party who prevails at trial by surprising their opponent with an unconventional strategy or undisclosed theory. If the verdict is reversed and a retrial ordered (a fact made more likely using an undisclosed position), then the party will have lost the element of surprise, locked in potentially adverse witness testimony, and substantially reduced their overall likelihood of success.

Lawyers and cryptologists practice very different professions. Despite their differences, a common thread ties them together—the need to share information while keeping secrets.

Kerckhoff’s Principle provides guidance on how to navigate that dichotomy for lawyers and cryptologists alike: Don’t confuse secrecy for quality; don’t fear disclosure of your system; assume your opponent will figure out your plans. By embracing these principles, lawyers can craft better positions, project greater confidence, and avoid defeat at the hands of a fully-informed opponent.

This article does not necessarily reflect the opinion of Bloomberg Industry Group, Inc., the publisher of Bloomberg Law and Bloomberg Tax, or its owners.

Author Information

Adam Adler is a trial and appellate attorney at Reichman Jorgensen Lehman & Feldberg, whose practice focuses on constitutional law, intellectual property, and creators’ rights.

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