More separation of the code

1 files changed, 39 insertions, 0 deletions

diff --git a/rsa/core.py b/rsa/core.py
new file mode 100644
index 0000000..f42801c
--- /dev/null
+++ b/rsa/core.py
@@ -0,0 +1,39 @@
+'''Core mathematical operations.
+
+This is the actual core RSA implementation, which is only defined
+mathematically on integers.
+'''
+
+import types
+
+import rsa.common
+
+def encrypt_int(message, ekey, n):
+    """Encrypts a message using encryption key 'ekey', working modulo n"""
+
+    if type(message) is types.IntType:
+        message = long(message)
+
+    if not type(message) is types.LongType:
+        raise TypeError("You must pass a long or int")
+
+    if message < 0 or message > n:
+        raise OverflowError("The message is too long")
+
+    #Note: Bit exponents start at zero (bit counts start at 1) this is correct
+    safebit = rsa.common.bit_size(n) - 2                   #compute safe bit (MSB - 1)
+    message += (1 << safebit)                   #add safebit to ensure folding
+
+    return pow(message, ekey, n)
+
+def decrypt_int(cyphertext, dkey, n):
+    """Decrypts a cypher text using the decryption key 'dkey', working
+    modulo n"""
+
+    message = pow(cyphertext, dkey, n)
+
+    safebit = rsa.common.bit_size(n) - 2                   #compute safe bit (MSB - 1)
+    message -= (1 << safebit)                   #remove safebit before decode
+
+    return message
+