Elgamal cipher key generator code - (initial)

Author: psyas

README.md

@@ -3,7 +3,7 @@
 ### All algorithms implemented in Python (for education)
 
 These are for demonstration purposes only. There are many implementations of sorts in the Python standard library that are much better for performance reasons.
-test
+
 ## Sort Algorithms
 
 

ciphers/elgamal_key_generator.py

@@ -0,0 +1,62 @@
+import os
+import random
+import sys
+import rabin_miller as rabinMiller, cryptomath_module as cryptoMath
+
+min_primitive_root = 3
+
+
+def main():
+    print('Making key files...')
+    makeKeyFiles('elgamal', 2048)
+    print('Key files generation successful')
+
+
+# I have written my code naively same as definition of primitive root
+# however every time I run this program, memory exceeded...
+# so I used 4.80 Algorithm in Handbook of Applied Cryptography(CRC Press, ISBN : 0-8493-8523-7, October 1996)
+# and it seems to run nicely!
+def primitiveRoot(p_val):
+    print("Generating primitive root of p")
+    while True:
+        g = random.randrange(3,p_val)
+        if pow(g, 2, p_val) == 1:
+            continue
+        if pow(g, p_val, p_val) == 1:
+            continue
+        return g
+
+
+def generateKey(keySize):
+    print('Generating prime p...')
+    p = rabinMiller.generateLargePrime(keySize)  # select large prime number.
+    e_1 = primitiveRoot(p)  # one primitive root on modulo p.
+    d = random.randrange(3, p)  # private_key -> have to be greater than 2 for safety.
+    e_2 = cryptoMath.findModInverse(pow(e_1, d, p), p)
+
+    publicKey = (keySize, e_1, e_2, p)
+    privateKey = (keySize, d)
+
+    return publicKey, privateKey
+
+
+def makeKeyFiles(name, keySize):
+    if os.path.exists('%s_pubkey.txt' % name) or os.path.exists('%s_privkey.txt' % name):
+        print('\nWARNING:')
+        print('"%s_pubkey.txt" or "%s_privkey.txt" already exists. \n'
+              'Use a different name or delete these files and re-run this program.' %
+              (name, name))
+        sys.exit()
+
+    publicKey, privateKey = generateKey(keySize)
+    print('\nWriting public key to file %s_pubkey.txt...' % name)
+    with open('%s_pubkey.txt' % name, 'w') as fo:
+        fo.write('%d,%d,%d,%d' % (publicKey[0], publicKey[1], publicKey[2], publicKey[3]))
+
+    print('Writing private key to file %s_privkey.txt...' % name)
+    with open('%s_privkey.txt' % name, 'w') as fo:
+        fo.write('%d,%d' % (privateKey[0], privateKey[1]))
+
+
+if __name__ == '__main__':
+    main()