Encryption

Encryption

Eavesdroppers, symmetric keys and the public and private key pair.

Transcript

When data crosses a public network, a hacker, called an eavesdropper, can intercept it.

Encryption turns data into a form that is unreadable to anyone it is not meant for. It cannot stop interception, but it stops the data making sense.

Symmetric encryption uses the same key to encrypt and to decrypt the message.

For example, shift every letter by three. Hello becomes Khoor, and shifting back reveals it. But both sides must share the key.

Asymmetric encryption uses two keys: a public key, known to everyone, and a private key, kept secret.

The sender shares the public key. The receiver encrypts with it, and only the sender's private key can decrypt.

One shared key, or a public and private pair. Either way, interceptors see only scrambled data.

More in this series

1:32

Data packets and packet switching

Packet structure, routing, out-of-order arrival and reassembly.

packetsrouters

1:19

Simplex, half-duplex and full-duplex

Which way the data flows, and when.

transmission mode

1:43

Serial and parallel transmission

Bits one by one or all at once, skew, crosstalk and USB.

serialparallelUSB

1:21

Error detection

Why errors happen, and checksums, echo checks and ARQ.

checksumARQ

1:13

Parity checks

Parity bits and parity blocks, including finding and fixing a flipped bit.

parityerrors

1:32

Check digits

The multiply, add, divide-by-10 method with a worked example and a practice question.

check digitworked example

5:08

Unit 2 quiz

Ten questions with a think-time countdown and explained answers.

quizrevision