EC El Gamal Tools

The following are tools to perform an Elliptic Curve El Gamal encryption.

Converting Letters to Numbers

Use the Text to Integer tools.

Find a prime number

If you are given a prime number, just put `p = …`

How to generate an elliptic curve in Sage over your prime field

The list is a list of coefficients: [0,a,0,b,c] for y^2 = x^3 + ax^2 + bx + c.
You can put the field of definition in the first spot, e.g. GF(7) or RR or QQ

Choose a point and give it a name

Determine the multiplicative order of your point

Random Number Generator

randint(a,b) gives an integer between a and b inclusive

Find a square root mod p

If this Sage command returns a number (the example is square root of 2 mod 7), you have successfully gotten a square root. If it returns something that has the string `sqrt` in it, it is telling you there is no square root in GF(p).

Take a multiple of a point