Added Playfair encryption

Author: KumarSashank

Cryptography/Playfair.py

@@ -0,0 +1,74 @@
+key='kumarsashank'
+matrix=[]
+key=key.upper()
+# print(key)
+distinct_key=[]
+for i in key:
+    if i not in distinct_key:
+        distinct_key.append(i)
+
+print('Distinct key: ',distinct_key)
+alphabets='ABCDEFGHIKLMNOPQRSTUVWXYZ' #Removed J
+temp=[]
+for i in distinct_key:
+    temp.append(i)
+for i in alphabets:
+    if i not in temp:
+        temp.append(i)
+matrix=[temp[0:5],temp[5:10],temp[10:15],temp[15:20],temp[20:25]]
+print('Playfair Matrix: ')
+for i in range(5):
+    print(matrix[i])
+
+
+text=input('Enter plain text: ')
+# text='Rak'
+text=text.upper()
+list_1=[]
+
+#making group of pairs 
+text=text.replace(' ','')
+list_1=list(text)
+# print(list_1)
+for i in range(len(list_1)):
+    if i%2!=0:
+        if list_1[i-1]==list_1[i]:
+            list_1.insert(i,'X')
+# print(list_1)
+if(len(list_1)%2!=0):
+    list_1.append('X')
+# print(list_1)
+
+#making pairs
+list_2=[]
+for i in range(0,len(list_1),2):
+    list_2.append(list_1[i:i+2])
+print('Pairs are: ',list_2)
+
+def find_position(temp,l):
+    for i in range(5):
+        for j in range(5):
+            if l[i][j]==temp:
+                return i,j
+
+#encryption
+cipher=[]
+
+for e in list_2:
+    p1,q1=find_position(e[0],matrix)
+    p2,q2=find_position(e[1],matrix)
+    if p1==p2:
+        cipher.append(matrix[p1][(q1+1)%5])
+        cipher.append(matrix[p2][(q2+1)%5])
+    elif q1==q2:
+        cipher.append(matrix[(p1+1)%5][q1])
+        cipher.append(matrix[(p2+1)%5][q2])
+    else:
+        cipher.append(matrix[p1][q2])
+        cipher.append(matrix[p2][q1])
+# print(cipher)
+
+str=''
+for i in cipher:
+    str+=i
+print('Cipher text: ',str)