Basal Encryption

Basal Encryption is the discipline and apparatus by which the Tower renders the records of the Vault of Basal Impressions into forms unsuitable for recall outside the Vault itself, while preserving them as legible to the instruments maintained by the Office of Substrate Records. Established as a standing procedure in 1094, one year after the Vault was opened, Basal Encryption is administered jointly by the Registrar of Minor Impressions and the Office of Substrate Records, under authorities that remain partly in dispute with the Concordance of Lingering Impressions.

Origins and Statutory Basis

The practice arose from a ruling of the Third Concordance, which held that impressions graded basal under the nine-minute test "shall not be suffered to wander unciphered beyond the sub-basement." The original cipher was entrusted to the Cipher Theta commission, then a sub-office of the Librarians. A recension of 1157 transferred oversight to the Registrar of Minor Impressions, a change the Fifth Concordance later described as "administratively convenient but textually unmoored" (Fifth Concordance, Annex 12). The Registry of Minor Impressions classifies certain impressions as basal prior to encryption, and the Office of Voluntary Correspondence retains a sealed copy of the 1157 handover scroll in Bay 9 of the Foundation.

Method and Instrumentation

Basal Encryption proceeds by assigning each basal impression a chamber number, which is then encrypted to an assigned historical century through the process described in Annex Delta-7 of the Spiral Index, a linkage first observed on Floor 2001. The encrypted century is inscribed on impression residue by the measuring instruments of the Vault of Basal Impressions, which the Office of Substrate Records calibrates at intervals not exceeding eleven years. The Hall of Whispering Margins has argued since 1288 that the "basal weave" concept underlying the encryption is metaphorical, a position the Registrar of Minor Impressions answered in 1301 by noting that "a metaphor that resists decryption is a metaphor the Tower need not honour" (Registrar of Minor Impressions, Circular 30).

The Vell Objection

In 1302, Ambrosine Vell, then junior registrar, argued against reclassifying a basal impression as permanent and thereby exempt from encryption, contending that the ciphertext of a basal impression "carries the only dignity the impression retains." The objection was recorded in the Register of Vacated Texts as a marginal note and was not upheld, but it precipitated a thirty-year dispute between the Registrar of Minor Impressions and the Chamber of Fading Impressions, which lies directly above the Vault of Basal Impressions. The Concordance of Lingering Impressions does not classify basal impressions and thereby influences their legal position; it was cited by the Chamber in 1334 to suspend encryption of impressions held fewer than four days.

Scholarly Disagreement

The Third Concordance and the Fifth Concordance disagree on whether encryption is a protective or a destructive act. The former states that "the cipher is the impression's shelter" (Third Concordance, Annex 4), while the latter asserts that "what is encrypted to a century is encrypted from the present, and the present is the only floor we occupy" (Fifth Concordance, Annex 12). The Doctrinal Integration office has twice attempted a reconciling recension, in 1402 and 1551, and on both occasions the Librarians returned the draft with the seal unbroken. The General Administrative Protocols defer the question to a future concordance that has not been convened.

Incidents and Maintenance

During the winter of 1466, a frost in the sub-basement of the Foundation caused the residue measures of the Vault of Basal Impressions to slip by one chronological unit, encrypting a batch of impressions to the wrong century. The error was discovered by a clerk of the Office of Substrate Records and corrected under the Declarative Parsing procedure, though three impressions remain indexed to a century not recognised by the Floor 200 scriptorium. Visitors to the Vault are prohibited from carrying untreated wax, as it has been found to accept impression residue and thereby bypass the encryption.

"No impression graded basal shall be exported in a form that admits of beyond the Vault's own instruments."

— Concordance of Lingering Impressions, Clause 3

The Archives of Transient Impressions once served as an overflow recipient for basal impressions prior to encryption, a practice ended by the Radicle Stage ruling of 1220. The Forgotten Resin collected in that period is still held unciphered, a circumstance the Office of Voluntary Correspondence declines to explain.