Crypto shocker: 'Perfect cipher' dates back to telegraphs

A computer scientist has unearthed evidence that a theoretically unbreakable form of cryptography was in use by telegraph operators as early as 1882, 35 years before its supposed invention by a duo from Bell Labs and the US Army.

The one-time pad, which is also known as the perfect cipher, uses a random key that is shared by both sender and receiver to encrypt and decode a sensitive message. Assuming the key is used only once and both parties securely dispose of it, the technique is the only known method to perform mathematically unbreakable encryption, according to this post by cryptography historian Dirk Rijmenants. Until now its invention was dated to 1917 and credited to Gilbert Vernam of Bell Labs and Captain Joseph Mauborgne of the Army Signal Corps.

But according to The New York Times, computer scientist Steven Bellovin recently found a description of the one-time pad algorithm in an 1882 telegraphers' codebook titled Telegraphic Code to Insure Privacy and Secrecy in the Transmission of Telegrams. It was written by one Frank Miller, a successful banker from California who went on to become a trustee of Stanford University. He also served in the US Army's inspector general's office, where he worked on a team investigating the assassination of Abraham Lincoln.

"A banker in the West should prepare a list of irregular numbers to be called 'shift numbers,'" Miller wrote. "The difference between such numbers must not be regular. When a shift-number has been applied, or used, it must be erased from the list and not be used again."

The NYT said independent specialists in cryptography have confirmed that Miller's work proves he developed the one-time pad long before its discovery and later patenting by Vernam and Mauborgne.

“Miller probably invented the one-time pad, but without knowing why it was perfectly secure or even that it was,” David Kahn, the author of the 1967 book The Codebreakers, was quoted as saying. “Moreover, unlike Mauborgne’s conscious invention, or the Germans’ conscious adoption of the one-time pad to superencipher their Foreign Office codes, it had no echo, no use in cryptology. It sank without a trace — until Steve found it by accident.”

A PDF of Bellovin's writeup in the July issue of the journal Cryptologia is here. ®