Example of El Gamal Criptography in Number

Picture above is an example of numerical calculation analogy ElGamal. Clark Kent was originally the public key (y), after he chose a private key is (x). Count y can be read in addition chaining post in this blog. after that Clark tells Lex Luthor key public.

Lex Luthor will send a character 'A' to Clark. Knowing Clark's public key and private key without knowing the property of Clark, he calculates chiperteks (a, b). ASCII characters with a code and b is sent to Clark. Clark chiperteks receive it. ago he was doing decryption by using a and b. plainteks that is' A ', the same as you want to send Lex Luthor

Number Of ElGamal

If all the prime factors of p - 1 are relatively
small, lots of cryptographic attacks are possible. Generally, primes p such that p-1 has a big prime
factor are much better.









Note: k; r can be computed before the message is seen. In addition, you need a new k and r
every time you sign a message. Otherwise, it will not be secure.







Digital Signature Algorithm (DSA)

Addition Chaining or Divide and Conquer for ElGamal Programing

Problems in the Calculations exponential and modulo in 'El Gamal' can be done using the manual counting or a calculator, but if the code is calculated in the program will generate a value of 0. this is because there is no data type in programming resource that can accommodate the data before these modulus. So to solve this problem some authors reduce the formula to calculate a and y.

vw mod p = [( v mod p )( w mod p )] mod p
example :



Method above in mathematics discreet technique called divide and conquer. Referred to as addition chaining technique because the results was carried out together with direct multiplication modulo operation. With this technique, the results will not reach a large number.

Besides the problem of y and a, the value of b also has a similar problem. Even in the calculation of b values before the integer modulus greater. This is because in addition to exponensial with a large number but also multiplied by the value of plain text blocks to mj. With divide and conquer method is also the formula b can be measured down

revealed to be:


From the equation above can be concluded that the value of mj is no need to be a factor during the process y^k mod p is calculated. Fair value multiplied later after y ^ k mod p is established, and then the new modulus with p more