Data commit

Task/Vigen-re-cipher/Ring/vigen-re-cipher.ring

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+# Project : Vigenère cipher
+
+key = "LEMON"
+plaintext = "ATTACK AT DAWN"
+ciphertext = encrypt(plaintext, key)
+see "key = "+ key + nl
+see "plaintext  = " + plaintext + nl
+see "ciphertext = " + ciphertext + nl
+see "decrypted  = " + decrypt(ciphertext, key) + nl
+
+
+func encrypt(plain, key)
+        o = ""
+        k = 0
+        plain = fnupper(plain)
+        key = fnupper(key)
+        for i = 1 to len(plain)
+             n = ascii(plain[i])
+             if n >= 65 and n <= 90
+                o = o + char(65 + (n + ascii(key[k+1])) % 26)
+                k = (k + 1) % len(key)
+             ok
+        next
+        return o
+
+func decrypt(cipher, key)
+        o = ""
+        k = 0
+        cipher = fnupper(cipher)
+        key = fnupper(key)
+        for i = 1 to len(cipher)
+             n = ascii(cipher[i])
+             o = o + char(65 + (n + 26 - ascii(key[k+1])) % 26)
+             k = (k + 1) % len(key)
+        next
+        return o
+
+func fnupper(a)
+        for aa = 1 to len(a)
+             c = ascii(a[aa])
+            if c >= 97 and c <= 122
+               a[aa] = char(c-32)
+           ok
+        next
+        return a