added naive SHA256 and RSA implementations

imp/crypto/hash.py

@@ -0,0 +1,7 @@
+import hashlib
+
+def sha256(data: bytes, as_bytes: bool = False) -> bytes:
+    hasher = hashlib.sha256()
+    hasher.update(data)
+    hash = hasher.digest()
+    return hash if as_bytes else int.from_bytes(hash)

imp/crypto/rsa.py

@@ -0,0 +1,18 @@
+'''
+Simplification of Euler's Totient function knowing
+the prime factorisation for the public key N value.  
+'''
+def _totient(p: int, q: int) -> int:
+    return (p - 1) * (q - 1)
+
+'''
+Implements RSA encryption as modular exponentiation. 
+'''
+def encrypt(plaintext: int, e: int, N: int) -> int:
+    return pow(plaintext, e, N)
+def decrypt(ciphertext: int, d: int, N: int) -> int:
+    return pow(ciphertext, d, N)
+
+def gen_private_key(e: int, p: int, q: int) -> int:
+    return pow(e, -1, _totient(p, q))
+