Is this quantum quagmire important? No... well... admittedly yes, since Prism baddies, Google now have their own Quantum computer to calculate things like how to read a Google user's mind, or get the drug patent for some exotic disease first. Lockheed Martin, who make the aircraft Western Powers use to undermine whoever has upset them last week. Yes, that Lockheed Martin, the largest defence firm in the planetary region, have one too.
So, public key encryption, which uses the fact that prime numbers such as 3, or 7, cannot be square routed, is pretty much useless against Quantum Computing, which has a penchant for such things. Also useless, all the other methods come up with by human beings, with the exception of one Russian technique, the only encryption method I have always considered as secure.
If you do encrypt your email, even in a field such as mine, the legal field, then you paint a red marker on your usage. The tyrannous powers of the powers of world espionage are not there to be trifled with. If you are not utterly certain you are safe, chances are you aren't. Russia, despite its prowess, uses typewriters to record all of their most secure information. I personally use longhand, at least these days.
BUT BACK TO ENCRYPTION.
Unencrypted emails tend to pass through the system. In South Africa all emails are stored permanently by providers for the government, but even then, they are mostly safe in the same way one wildebeest in a migration across the Serengeti has safety on its side. Yes, it is vulnerable, but it acts like every other Wildebeest, it does not draw attention to itself. Encryption, means you are a target, unless of course your encryption is impossible to decipher, even with a quantum computer.
In the legal field, we still generally use the physical courier services that many have waylaid. But with our clients, we often communicate by email and by telephonic means.
I have suggested that robotic drone technology is approaching a point, where technology can be averted all-together, and a drone used in lieu of a physical courier for everyday usages, with longhand messages of course. If the major software manufacturers are working with the espionage infrastructure, then chances are everything on your internet connected digital device is already vulnerable. Russia understands this.
The one method of encryption that is impossible to decrypt without the key on the other side, was named the One Time Pad System. Yes, it is the system which appears in my spy novel based on the apartheid spy versus spy real life stories I was told as a child. In my book I just so happened to use inventive ideas such as the use of DNA, I would not do so in the modern world. DNA can be too easily accessed these days.
One time pad encryption relies on the constitution of a truly random string of digits, which are used to transform and only once transform, another string of communication.
Let us use the 'random string' (it isn't really) of 00 11 22 33 44 55 66 77 88 99 01 02 03 03 04 05;
And let us encode a message with it: Marc is encrypting.
So to use the classical Russian method we write: marcisencrypting.
Then each letter is substituted with a number, let us say A = 1. B = 2.
M = 13, a = 1, r = 18, c = 3, i = 9, s = 19, e = 5, n = 14, c = 3, r = 18, y = 25, p = 16, t = 20, i = 9, n = 14, g is 7.
so we have:
13 01 18 03 09 19 05 14 03 18. 25 16 20 09 14 07
And we add these with our random numbers: add: 00 11 22 33 44 55 66 77 88 99 01 02 03 03 04 05 to is, and get:
13 12 40 36 53 74 71 91 91 17 (technically 117, but we change mod our numbers by 100) 26 18 23 18 12
13 12 40 36 53 74 71 91 91 17 26 18 23 12 18 12
This is sent to someone with the one time pad of say: 00 11 22 33 44 55 66 77 88 99 01 02 03 03 04 05.
They then reverse the process we followed. For instance, 13 minus 00 = 13, which is m. 12 minus 11 is 1 which is a, 40 minus 22 is 18, which is r, 36 minus 33 is 3 which is c. Marc. 53 minus 44 is 9 which is i, 74 minus 55 is 19 is s, 71 minus 66 is 5 is e, 91 minus 77 is 14 = n, 91 - 88 = 3 which is c, 17 minus 99 is - 82 which being a minus number we add one hundred to giving 18 which is r, 26 minus 01 is 25 which is y, 18 minus 02 is 16 which is p, 23 minus 03 is 20 which is t, 12 minus 03 is 9 which is i 18 minus 04 is 14 which is n, 12 minus 05 is 7 which is g.
Suddenly we have a message only the receiver can read: marcisencrypting, which can then be given spaces either randomly or according to some encrypted message on spacing and capitalisation, using the same technique: so say: Marc is encrypting.
The problem is with random order and reuse. If you program a system to create random numbers, most languages just use a public key system which isn't random. Here, I likewise used a system purposely not random. The repeated digit was due to a typing error, where I skipped a letter in manually encrypting, and was too lazy to redo those after it. But if I used that code, I could never reuse it. The Russians began reuse of One Time pads during the cold war, which allowed Americans to decrypt those messages.
One Time Pad, prior to the Public Key system, which latter is safe given the many years a current PC takes to decode it, used to be the standard for corporations for internal communications. With quantum computing and supercomputers spying on everyone with such success, it is perhaps time to return to the only sure method.
How you generate a truly random number without relying on public key short cuts in square roots of numbers which cannot be square rooted is up to you.