crypto: add a few more challenges

crypto/basic_mod1/message.txt

@@ -0,0 +1 @@
+128 322 353 235 336 73 198 332 202 285 57 87 262 221 218 405 335 101 256 227 112 140 

crypto/basic_mod1/solve.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+
+# Take each number mod 37 and map it to the following character set: 0-25 is the alphabet (uppercase), 26-35 are the decimal digits, and 36 is an underscore.
+
+with open('message.txt') as file:
+    content = file.read().strip()
+
+print("picoCTF{", end="")
+for n in content.split(' '):
+    number = int(n)
+    number %= 37
+    if number < 26:
+        print(chr(number + ord('A')), end="")
+    elif number >= 26 and number < 36:
+        print(number - 26, end="")
+    elif number == 36:
+        print('_', end="")
+    else:
+        print()
+        print(f"Code author seems to have forgotten a number.... {number}")
+        exit(1)
+print("}")