Introduction to Cryptography with Coding Theory, 3rd Edition

A.7 Examples for Chapter 9

Example 22

Suppose you need to find a large random prime of 50 digits. Here is one way. The function NextPrime[x] finds the next prime greater than $x$. The function Random[Integer,{a,b}] gives a random integer between $a$ and $b$. Combining these, we can find a prime:

In[1]:= NextPrime[Random[Integer, {$10\hat{\phantom{a}}49$, $10\hat{\phantom{a}}50$ }]]

Out[1]= 73050570031667109175215303340488313456708913284291

If we repeat this procedure, we should get another prime:

In[2]:= NextPrime[Random[Integer, {$10\hat{\phantom{a}}49$, $10\hat{\phantom{a}}50$ }]]

Out[2]= 97476407694931303255724326040586144145341054568331

Example 23

Suppose you want to change the text hellohowareyou to numbers:

In[3]:= txt2num1["hellohowareyou"]

Out[3]= 805121215081523011805251521

Note that we are now using ...