Code (cryptography) in the context of "Cryptanalysis"

The Invitation to William was a letter sent by seven Englishmen (six nobles and a bishop), later referred to as "the Immortal Seven", to stadtholder William III, Prince of Orange, dated 30 June 1688 (Julian calendar, 10 July Gregorian calendar). In England, the heir apparent to the throne, James Francis Edward Stuart, had just been born to the unpopular King James II of England, and baptised a Catholic. The letter asked William, who was a nephew and son-in-law of James II, to use military intervention to force the King to make his eldest daughter, Mary, William's Protestant wife, his heir. The letter alleged that the newborn prince was an impostor.

The letter informed William that if he were to land in England with a small army, the signatories and their allies would rise up and support him. The Invitation briefly rehashed the grievances against King James. It claimed that the King's son was supposititious (fraudulently substituted) and that the English people generally believed him to be so. The present consensus among historians is that he was almost certainly their real son. The letter deplored that William had sent a letter to James congratulating him for the birth of his son, and offered some brief strategy on the logistics of the proposed landing of troops. It was carried to William in The Hague by Rear Admiral Arthur Herbert (the later Lord Torrington) disguised as a common sailor, and identified by a secret code.

In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography.

Codes generally substitute different length strings of characters in the output, while ciphers generally substitute the same number of characters as are input. A code maps one meaning with another. Words and phrases can be coded as letters or numbers. Codes typically have direct meaning from input to key. Codes primarily function to save time. Ciphers are algorithmic. The given input must follow the cipher's process to be solved. Ciphers are commonly used to encrypt written information.

A diplomatic cable, also known as a diplomatic telegram (DipTel) or embassy cable, is a confidential text-based message exchanged between a diplomatic mission, like an embassy or a consulate, and the foreign ministry of its parent country. A diplomatic cable is a type of dispatch. Other dispatches may be sent as physical documents in a diplomatic bag.

The term cable derives from the time when the medium for such communications was telegraphs travelling along international submarine communications cables, though over time they have progressed into other formats and pathways. The term cablegram is also sometimes used. Due to the importance and sensitive nature of the subject matter, diplomatic cables are protected by the most elaborate security precautions to prevent unfettered access by the public or unauthorized interception by foreign governments. Generally digital in format, they are always encrypted, frequently by unbreakable one time pad ciphers using key material distributed using diplomatic couriers.