Cryptography’s “Avoid History” Rule

Cryptography’s “Avoid History” Rule is the unwritten professional prohibition against letting the history of ciphers guide modern cryptographic work. It arises from a paradox: earlier ciphers may contain clues to present ones, but studying them can also plant misleading patterns in the mind, compromise the distinctiveness of new systems, or draw a cryptographer into a maze from which there is no clear way out. Rong Jinzhen’s deliberate challenge to the rule becomes a test of whether historical knowledge is a dangerous distraction or a path to discovery.

The Rule and Its Rationale

The rule applies to both people who create ciphers and people who decrypt them. In the account of Rong Jinzhen’s work, its rationale is not that the past has nothing to teach. On the contrary, historical concepts and theories can exert a powerful attraction: once a cryptographer begins following one, it may redirect attention and impair the work at hand. The danger lies in the mind’s readiness to find connections, especially in a field where a resemblance between systems can become a vulnerability.

For cipher creators, the requirement is to eliminate signs of a cipher’s history. If two systems share an exploitable similarity, breaking one may help break the other. The rule therefore demands more than caution about old examples: it makes separation from precedent part of security. Ciphers must not offer an opponent an easy bridge from a known solution to a new one.

The Forbidden Historical Path

Rong Jinzhen advances a contrary premise in Cryptography’s two-paths theory. He sees ciphers as connected across time: systems used in history and those used in the present may have an invisible relationship, and ciphers developed during the same period may also be closely linked. On this view, the solution to a cipher under examination might be concealed in an earlier one. History is not merely background; it is a possible source of analytical leads.

This approach would have Rong Jinzhen move through successive layers of cryptographic development in search of underlying principles. Each layer offers ideas that could help narrow a search, but also theories capable of taking hold of his attention and making his work useless. His method is therefore presented as a wager on two opposing possibilities: historical comparison might eliminate candidate paths, or it might entrap the investigator among patterns that lead nowhere.

The Safer Method and Its Limits

The conventional procedure described in the book starts with information gathered by intelligence agents. Cryptographers use that material to form hypotheses, then construct and test possible keys against possible cipher structures. The image is of making keys and doors in potentially limitless numbers; the practical scale depends on how much information is available and how perceptively the investigator responds to the particular cipher.

The method is acknowledged to be simple and laborious, but its very caution makes it safer and, especially for high-level ciphers, effective. It keeps the work tied to available evidence rather than allowing historical analogy to dictate its direction. Against this measured process, Rong Jinzhen appears to rush into forbidden territory: he is not content to proceed by elimination but wants to use prior generations’ work as a vantage point from which to search more widely.

Rong Jinzhen’s Deliberate Breach

When Jan Liseiwicz encounters Rong Jinzhen’s historical diagrams and hears his account of the theory, he recognizes that the rule has been broken. He cannot tell whether Rong Jinzhen is unaware of the danger or understands it and has chosen to proceed regardless. The circumstances lead him toward the latter interpretation: Rong Jinzhen’s use of historical material appears deliberate, not an error born of ignorance. At that point Rong Jinzhen has spent less than six months in the cryptography unit.

Jan Liseiwicz responds not with a straightforward rebuke but with silent admiration, mixed with jealousy. He sees Rong Jinzhen as pursuing an unusually hazardous line of thought while fully aware, or seemingly aware, of its risks. The uncertainty matters: the same conduct might belong to a genius who trusts exceptional capacities or to a reckless investigator who does not grasp the danger. Jan Liseiwicz cannot yet decide which description fits, and allows for the possibility either of astonishing achievement or of failure and tragedy.

Results, Risk, and Professional Isolation

Rong Jinzhen later decrypts PURPLE without telling anyone. Jan Liseiwicz’s retrospective account presents that success as a source of relief and admiration, but also as evidence of how close the work had come to going wrong. Suggestions Jan Liseiwicz had sent about decrypting PURPLE were mistaken. The team’s decision not to let Rong Jinzhen see those letters meant that he did not follow their misleading direction; what had seemed unfair in the moment proved fortunate for the attempt. His success thus does not establish that historical inquiry is generally safe. It shows instead how uncertain the consequences of guidance and exclusion can be in a field where a wrong path may consume the whole effort.

The rule also carries a cost beyond technical risk. The history of cryptography is described as a lonely forest in which investigators cannot safely ask earlier workers for directions or simply build on their conclusions. Later cryptographers lose a shared intellectual inheritance because the concepts that might connect generations can also compromise their work. The prohibition protects ciphers by isolating them from precedent, but it leaves practitioners facing closed paths and traps without the ordinary support of accumulated knowledge.

Rong Jinzhen’s breach makes that contradiction visible. If history contains clues, avoiding it may mean discarding useful routes; if those clues become intellectual traps, pursuing them may destroy the investigator’s effectiveness. The rule is therefore not a simple rejection of the past but a discipline founded on fear of its influence. His encounter with PURPLE gives that discipline its sharpest test: success is possible beyond the forbidden boundary, but the boundary remains dangerous even when crossed by exceptional talent.