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In late 1997, the history of public-key cryptography was turned around with the announcement (then extended) that

An account of these discoveries is given in a 1987 note [5] by J. H. Ellis: The History of Non-Secret Encryption; this is my rendering of an April 1998 ps archive, and is very similar to this document obtained from the NSA by FoIA case #19136 (narrative).

This calendar of event is confirmed by the December 1977 document [6] by J. H. Ellis: The Authentication Problem, obtained (with references redacted) in the same FoIA case, containing:

Non-Secret Encryption has now reached the phase where it is being considered for possible applications, and I find that many people are worried that the danger of spoofing may make its use untenable.

There is a writing by Simon Singh (in the The Code Book) about J. H. Ellis, C. C. Cocks, M. J. Williamson, and the coming out of the story.

All versions of documents [1]..[5] that I could locate (in 2014) are clearly re-typesettings (with the possible exception of the FoIA source for [5]). Ross Anderson hypothetized that there might have been alterations in the declassification process as an attempt to deny the existence of the then-secret GCHQ by re-attributing the documents to the CESG.

Also, I observe a discrepancy between an indication about [2] given in [3] by M. J. Williamson:

The information rate of the system is low in that 3 bits are broadcast for every 1 of the message. (The ratio in the method of [2] is 2 for 1).

and [2] as we read it, where there is nothing suggesting a significant expansion of plaintext to ciphertext; which in modern terminology is per textbook RSA, with public exponent equal to the modulus, and splitting of message in ECB mode:

The sender has a message, consisting of numbers $C_1$, $C_2$, $\dots$ $C_r$ with $0 < C_i < N$
He sends each, encoded as $D_i$ where $D_i = C_i^N$ reduced modulo $N$.

This opens a possibility that the author of [3] had access to material about [2] different from what we have (perhaps, more extensive than the remarkably terse version that we know). For example it could be that M. J. Williamson considered a single $C$, and the overhead related to $N$, as would be natural if $C$ was the key to another cryptosystem.

Are there public verbatim copies of any of the originals, or hope to obtain these?

Also: Is there an account of the circumstances of the early diffusion of any of these documents?

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My wishes largely came true! The GCHQ (briefly) published scans of [1] and [2], and another 1970 document:

These scans are excellent, including [2s] which seems to be from a printout of an earlier scan (as visible on an apocryphal annotation on bottom of the second page). The typeset versions of [4] and [1] are very close to [1s] and [2s]; differences are in formatting, typography, and a few transcription typos, like [4] randomly uses MI or M1 where [1s] consistently uses M1.

[1.5s] studies an analog communication over metallic wires trying to resist eavesdropping. It is readily admitted the system is insecure. As apparent to an electronic engineer (even of the 1970s), if an eavesdropper is able to measure both voltage and current on the wire, s/he can break the system.

All in all: it is nice to have these verbatim, but I found nothing that was not essentially known before on the history of public-key cryptography as we know it.

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