1. Security Security is critical in the storage and transmission of information loss of information can not only cause problems to the organisation but can also incur legal penalties e.g. loss of laptops, CDs, etc. by public bodies or organisations working for them.

2. Symmetric (private key) encryption both ends use the same private key

3. Computers use mathematically generated digital keys (e.g. Generated from a password) and the encryption algorithms can be very fast e.g.TrueCrypt which can encrypt/decrypt hard disks 'on the fly', i.e. you don't notice any slow down in disk access Encryption time depends on length of key but longer keys are harder to break Problem – both ends have to have same key How can we transmit it ? Email, phone, text message? If a 100 people send secure messages to each other we need 4950 different keys

4. Asymmetric (public key) encryption Public key to lock the box (anyone can have it) Private key to unlock the box (I keep this)

5. To use asymmetric encryption we generate two mathematically related keys Public key used to encrypt files you can email this to anyone or put it on your web site, etc, etc People use this to encrypt files and send them to you, e.g. using email Private key (you keep this secret) which you use to decrypt files you receive

6. See http://www.thefreecountry.com/security/encryption.shtml