Lec 2: Authentication & Basic Cryptography

All people must have authentication for identification allows one party (the verifier) to gain
assurances that the identity of another (the claimant) is as declared, thereby preventing impersonation. The most common technique is by the verifier checking the correctness of a message (possibly in response to an earlier message) which demonstrates that the claimant is in possession of a secret associated by design with the genuine party. Techniques which provide both entity authentication and key establishment are often integrated, Other names: entity authentication, identity verification


Cryptography to increase privacy:

There are two basic methods for data encryption:
- Symmetric key cryptographydata is encrypted and decrypted with the same key. the strength of encryption depends on the size of the key: a key with less than 40 bits is to be considered insecure, while a key with more than 128 bits is fairly unbreakable.the problem is: how get both parties the secret key in the first place

-Public key cryptographypublic key cryptography requires two keys, a secret ("private") key and a well known ("public") key. there are two different scenarios where public key cryptography may be used:
1. Send a secret message that only a particular receiver shall be able to read:the sender encrypt the message with the receiver's public key, only the holder of the corresponding private key can decrypt an read the message.
2. Digital signatures:the author of a document encrypts the text with his private key. anyone who knows the authors public key can decrypt and read the message, this reliably authenticates the author.