Schematic SSL session setup

a. Back to TLS session setup

b. Abstract TLS (simplified)

c. Properties

The Turing Solution - BBC Archives

Alan Turing, born June 23 1912, is famous for his key role in breaking German codes in World War 2. But for mathematicians, his greatest work was on the invention of the computer.

Alan Turing's brilliance at maths was spectacular. Aged 22, just a year after his graduation, he was elected a fellow of King's College Cambridge. And it was just a year after that, that he turned his attention to problems in the foundations of mathematics and ended up showing that a simple machine, set up to read and write numbers and to run a few basic functions, could in principle do all the things that are do-able in mathematics. His 'universal' machine was just a concept - a paper tape that could be read, interpreted and acted on robotically. But the concept was profound.

World War II shortly afterwards took Turing's talents into other directions, but even while designing machines at Bletchley Park to break the German Enigma codes, he was wondering how much more a computing machine might do - play chess for example.

And although the war work might have delayed Turing's academic work, it greatly accelerated progress in electronics, so that in 1945 he returned to his first love, creating a complete design for what he expected to be the world's first fully programmable computer, the National Physical Laboratory's ACE - the Automatic Computing Engine. In the end, beset by hesitation and bureaucratic delays, the ACE was overtaken by a rival team in Manchester, whose Small Scale Experimental Machine first ran on June 21 1948. But the Manchester Baby, as it became known, fulfilled the requirements laid down in Turing's seminal 1936 paper, and in a handful of instructions had the power to do any kind of maths, or data processing, like a computer of today does.

Turing soon joined the Manchester team, and again with remarkable prescience started work on artificial intelligence, wondering whether electronic machines could programmed not just to do maths, but to think in the way human minds do - a hot topic of debate even now.

Those explorations were cut short by his suicide in 1954, following prosecution for his homosexuality. His death at a time when official secrecy still hid his code-breaking work, and when the history of computing was already being written meant that few appreciated his central role in today's dominant industry. But some enthusiasts hope they can write him back in where he belongs.

Digital Signatures

a. Digital Signatures

b. Digitatl Sigs. from Trapdoor Functions

c. Certificates: bind Bob's ID to his PK

d. Sample Certificate

Cyber Spies - BBC Archives

The criminal exploitation of the internet poses one of the biggest threats to UK national security. As organised crime gangs and terrorists use it to communicate and plan their activities, the police and security agencies are turning to hacking to conduct surveillance and gather intelligence.

In the first of a new series, File on 4 looks at the covert techniques being used to get beyond the firewall of a suspect's PC. But are the tactics legal? One leading expert says the rules governing interception are inconsistent and on occasions, misinterpreted by the police.

Reporter Stephen Grey also examines the way British companies are helping to proliferate this hi-tech snooping to countries with questionable human rights and which use it to monitor political opponents and dissidents.

And, with the Ministry of Defence developing its defences against sophisticated international attacks how vulnerable is the UK to "cyber warfare". Why did a Chinese state telecommunications company briefly 'hijack' most of the world's internet traffic one day last year?

Public Key Encryption

a. Public-Key Encryption

b. Building Block: trapdoor permutations

c. Example: RSA

d. Public Key Encryption with a TDF

Cryptography - BBC Archives

Melvyn Bragg and guests discuss the origins and history of codes. In October 1586, in the forbidding hall of Fotheringhay Castle, Mary Queen of Scots was on trial for her life. Accused of treason and denied legal representation, she sat alone in the shadow of a vast and empty throne belonging to her absent cousin and arch rival Elizabeth I of England. Walsingham, Elizabeth’s Principal Secretary, had already arrested and executed Mary’s fellow conspirators, her only hope lay in the code she had used in all her letters concerning the plot. If her cipher remained unbroken she might yet be saved. Not for the first time the life of an individual and the course of history depended on the arcane art of Cryptography.

What are the origins of this secretive science? And what links the ‘Caesar Cipher’ with the complex algorithms which underpin so much of our modern age?

With Simon Singh, science writer and author of The Code Book: The Secret History of Codes and Code-Breaking; Professor Fred Piper, Director of the Information Security Group at Royal Holloway, University of London and co-author of Cryptography: A Very Short Introduction; Lisa Jardine, Professor of Renaissance Studies at Queen Mary, University of London and author of Ingenious Pursuits.

Authenticated Encryption

a. Combining MAC and ENC (CCA)

b. Standards (at a high level)

c. Implementations problems: side channels

d. Generating Randomness (e.g. keys, nonces)

Tracking Cyber Attacks - BBC Archives

Security expert Dave Garfield explains some simple techniques that can be used to track cyber attacks and how attack tasks appear to be split between different groups with different skill sets.

Message Integrity

a. Message Integrity: MACs

b. Secure MACs

c. Construction: ECBC

d. Construction: HMAC (Hash MAC)

e. Construction: PMAC - a parallel MAC

GCHQ Cracking the Code - BBC Archives

The BBC's Security Correspondent Gordon Corera gains unprecedented access to Britain's ultra secret listening station where super computers monitor the world's communications traffic and Britain's global eavesdropping and electronic surveillance operations are conducted.

The layers of secrecy which have surrounded GCHQ's work are peeled away - what exactly does it do and who is it listening to?

The programme explores the wide area covered by signals intelligence - from looking for terrorists planning attacks against the United Kingdom to supporting military operations of the type underway in Afghanistan.

A team from the Counter terrorism section describes what it is like to listen in on terrorists' conversations and the constant battle to predict where the next attack will come from: "I don't think you would be human if you didn't go home at night and couldn't switch off and thought 'Oh my God. What happens if . . .?'" What about the ethics of eavesdropping and how does their work compare to the way it is portrayed on television in series like 'Spooks'?

Code-breakers talk about their work, attempting to find a chink in the armour of a carefully encrypted message sent by a terrorist or a foreign government. "It just feels amazing really," when there is a breakthrough, says one. "I mean you feel like you've won".

The programme looks at the technological challenges posed by the internet and the threat of cyber warfare, which has led to the establishment of a new cyber operations centre at Cheltenham. It also explores the scientific and mathematical breakthroughs which have been achieved at GCHQ, including the discovery of public key encryption, used when we shop on the internet.

There's a tour of the building's four great computer halls, containing racks and racks of IT equipment and covering around ten thousand square metres. "I could actually fit Wembley football pitch into three of the halls quite comfortably,' says the man in charge of making sure that the equipment doesn't crash.

Gordon Corera challenges the director Iain Lobban. There has been considerable speculation about whether the government is planning huge databases at GCHQ to keep track of all communications and internet traffic. Do they really spy on us? And how accountable are they?