Encryption: a very brief tour

David Furphy
Jul 22, 2017 · 3 min read

Encryption is now critical everyday to our work, economic, social, family and private lives. Quite reasonably, communities and governments want to stop abhorrent criminals like terrorists and pedophiles using encryption to hide their crimes. Yet for most of us (including most politicians and public servants) encryption is a complete mystery and we have no idea if this can be done and if there might be unintended consequences.

Here’s a quick tour of some basic facts that may help you understand the significance of encryption and the policies that may change the way its used.

A US Navy version of the Turing Bombe machine used during WWII to break the German’s Enigma ciphering machine and alter the course of the war.

Cryptography

  • is the art and science of writing secret messages often by scrambling words and letters
  • Cryptographic techniques and knowledge have been advancing for several thousand years
  • Encryption takes a message and uses some procedure or cipher (noun) to scramble it in a way that is difficult to unscramble unless you are the intended recipient who knows the details of the cipher used.
  • Many ciphers require some special “key” shared between the sender and the receiver
  • All these terms have the same meaning: encrypt, encode, cipher (verb), cypher, scramble (colloquial)
  • And these describe the reverse process: decrypt, decode, decipher, decypher, unscramble
  • Cracking or breaking a cipher is the task of working out how to unscramble a message without having authorised access to the details of the cipher and/or the special “key”
  • Some cyphers are provably unbreakable, such as the one-time pad cipher, even with a working quantum computer which may one day exist
  • A “strong” cipher is one that’s practically impossible to break with currently available technology

Public key encryption

  • developed in the 70’s allowed a cipher key to be safely shared in public
  • The Diffie-Hellman and RSA public key ciphers and a few later refinements allow all of todays secure banking and commerce, international diplomacy, movie streaming, web surfing, and chat apps for work and play.
  • Despite unimaginable increases in computing power over the last 40 years, variants of these ciphers remain practically unbreakable.
  • These ciphers allow private communication between 2 people or devices without needing or allowing any 3rd party to have access to the keys and thus is called “end-to-end encryption”
  • These ciphers utilise a few very well understood mathematical ideas including: the prime factorisation problem, the discrete logarithm problem, Eulers theorem, and Fermat’s little theorem

Backdoor

  • is a vague term for any persistent method of accessing messages without the permission of the sender and receiver
  • A backdoor may rely on flaws in the encryption system discovered or secretly introduced by those (law enforcement or criminals) wanting access.
  • Another type of backdoor involves 3rd parties (service providers, government or their agents) holding and providing mandated access to additional keys to the encryption.
  • A third type of backdoor doesn’t interfere with the end-to-end encryption, but instead gives authorities secret access (legal or otherwise) to the unencrypted messages sitting on the devices of the sender or receiver.
  • Communities and their law enforcement authorities don’t want bad guys using end-to-end encryption to keep their communications hidden.
  • Many community members are willing to allow “backdoor” access by law enforcement authorities to their communications if it means the bad guys are prevented from or caught doing bad things.
  • Cryptography and security experts agree that the great challenge with implementing any backdoor is preventing other bad guys from also using it to access our communications.
  • Many experts say it is not just hard, but impossible with current known cryptographic systems.
  • Arguments about government mandated backdoors flared in the 90’s and many thought technical and pragmatic arguments had triumphed by the turn of the millenium.

Knowledge

  • of strong end-to-end encryption systems is now so widely known and so easily accessed and implemented, that communities and law enforcement authorities will be tragically disappointed if they think they can solve terrorism, pedophilia and other abhorrent crimes by restricting access to unbreakable encrypted communications

Given the limited effectiveness and possible unintended consequences of messing with crypto-systems, scarce public resources would be better spent on other crime fighting endeavours such as targeted phishing attacks, human intelligence gathering and education.

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