1. Cryptology

2. Cryptology can be assigned to science until the twentieth century
Cryptology can be assigned to science until the twentieth century. It covers sections Cryptography - secret writing with characters and cryptanalysis - analysis of cryptography.     This is an ancient art and new science: even Julius Caesar used it, but only since the 1970s it was the object of scientific academic research.

3. William Frederick Friedman
The term cryptology is created by Friedman. He developed a statistical method (Friedman test) to encrypted text can be viewed through the language specifics to reach the key to them. The method was published in 1920 and is used in linguistics and reading the encrypted historical writings.
William Frederick Friedman

4. Criptology
Cryptanalyses
Cryptography
Key management
Simmetric
cryptosystem
Asimmetric
cryptosystem
Sistems for
Electronic
signature

5. Cryptanalysis
Cryptanalysis (from the Greek κρυπτός - hidden analysis) - the science of methods of obtaining the initial meaning of encrypted information without available secret information (key). In most cases, it being understood find, discover the key. In non-technical sense, cryptanalysis is to break the code (the code).

6. Cryptography
Cryptography (from the Greek words κρυπτός, kriptos - "hidden" and γράφω, column - "write") is a science that deals with the theory and practice of hiding information. Today, cryptography is considered a branch of both mathematics and computer science and is closely related to information theory, computer security and engineering work.

7. Symmetric cryptosystem
In symmetric cryptosystem using the same key for encryption and decryption of information. This key must be known to both parties - the one that encrypted information, and this, which shall decipher. There is secure storage, distribution and periodically update these keys between users of a symmetric cryptosystem .
Ciphertext
Sourece text
cryptosystem
key

8. Encryption
Decipherment
A B C ..
& J G.
A B C .
Input
Encrypted
information
Output
Encryption key (Ka)
Ka=Kb
Decipher key (Kb)

9. Asymmetric cryptosystem
In an asymmetric cryptosystem need for secure storage of public keys dropped, they are exchanged freely by users or published on Web sites .

10. advantages:
Key pair (public and private) can be used long time - several years;
Unlike the symmetrical network with N the number of participants supported keys is equal to the number of participants;
Allow the construction of reliable and efficient scheme for digital signatures and verification of data.
disadvantages:
Significantly slower compared with symmetrical; When using the encryption key is much longer than that of symmetrical;

12. Electronic signature system
Electronic signature algorithm used for encryption, one degree more secure than algorithms using hash function for authentication of the sender. Used asymmetric cryptography key pair - private and public, with one to encrypt and decrypt with the other.

13. Polina Staikova 12 a class SOU “Zheleznik” Stara Zagora
Created by :
Polina Staikova 12 a class
SOU “Zheleznik”
Stara Zagora