The Rule Separating Cryptographic Creation from Decryption

The Rule Separating Cryptographic Creation from Decryption is an unwritten principle that divides cryptographers into creators of ciphers and those who crack them. It presents the two pursuits as competing commitments of the mind, not simply as different technical tasks, and gives the work of concealing and uncovering information a deep professional and personal cost.

The Rule and Its Logic

The rule is stated plainly: an individual can either create ciphers or crack them, because whichever path a person takes, that person’s heart and mind have already been given over to the work. The principle treats cryptographic labor as an absorbing vocation whose demands leave no room for a second, equivalent allegiance. It also asserts a constraint beyond individual choice: the world does not allow two similar ciphers to exist. The account presents this as an unwritten rule of the field, rather than as a formal regulation enforced by an institution.

Its logic is therefore both psychological and structural. Creation and decryption face in opposite directions: one constructs a system intended to conceal messages, while the other seeks a way through that concealment. The rule describes these as mutually exclusive paths, but it does not offer a technical proof that a person could never change roles; its emphasis is on the total commitment each path requires and on the incompatibility of similar ciphers.

The Work of Decryption

The rule’s weight becomes clearer against the ordinary method of codebreaking. Intelligence agents first gather relevant information; cryptanalysts then use it to form hypotheses, testing possible keys against possible openings. The process resembles trying keys against doors, except that both the keys and the doors must be designed by the investigators. Its scale depends on how much material is available and how sensitive the analyst is to the cipher. Though described as a crude process of elimination, it is also presented as the safest and most effective method, particularly against a high-level cipher.

This work makes time and small defects consequential. The account likens cryptography to making use of every second and every inch: a cipher may seem seamless, yet its use can produce errors that disclose an opening. Those slips give the codebreaker a narrow chance to enter the cipher’s hidden structure. Against BLACK, however, Rong Jinzhen waited through countless days and nights without finding an error. His failure is presented as an unusual reversal, especially after the successful cracking of PURPLE had made the organization feel invulnerable.

Creation, Secrecy, and Military Use

The separation between making and breaking ciphers also sits within the work’s larger stakes. Director Zheng rejects the assumption that Rong Jinzhen’s importance lay chiefly in the country’s nuclear program: he describes the cryptographer’s work as a way of observing an opponent and uncovering its most guarded secrets, with greater practical military value than a nuclear weapon. In that account, codebreaking is not an abstract contest alone; what can be read or concealed may affect the balance between adversaries.

The novel also places cryptographic work beside broader questions about research and its uses. In a farewell letter, Jan Liseiwicz advises that Rong Jinzhen might devote his talents to artificial intelligence, a field he considers both practically valuable and capable of producing consequences its creators cannot control. He describes having abandoned his own ambition to pursue that research at the command of the Jewish people. This is not the cryptographic rule itself, but it echoes its concern with how a person’s work claims a life and with how knowledge, once created or applied, can exceed its maker’s intentions.

BLACK and the Apparent Exception

BLACK’s eventual solution complicates the image of an impenetrable cipher without overturning the rule. The narrator recalls working in an underground office in a mountain cave and using a calculator capable of more than 40,000 calculations to test an unlikely assumption. The key, the account reveals, was zero. BLACK had seemed firmly locked, but its barrier was only a façade: the door opened with a push rather than with a key that had to be discovered through an extended search.

The discovery belongs to the narrator’s account, not to Rong Jinzhen’s achievement. The later clarification is explicit that BLACK was not deciphered by Rong. This distinction matters to the rule: the startling solution does not show Rong crossing from codebreaking into cipher creation, or a cipher creator personally defeating his own system. Instead, BLACK’s zero key exposes the danger of mistaking apparent complexity for a genuinely locked system, while leaving intact the story’s separation of cryptographic roles.

Significance

The rule gives cryptography the shape of a divided vocation. Its practitioners work alone with an adversary’s hidden design, and success in one direction does not automatically confer power in the other. The methodical search through possible keys, the long failure against BLACK, and the eventual discovery that its key was zero together make the principle more than a maxim: they show how much the work depends on a person’s chosen orientation, and how easily certainty about a cipher can collapse when its apparent lock is false.