[fsbl] add fsbl for cv181x/cv180x

Change-Id: I6809bc5016d4bc148f62be2ed3f8e928ec111f19

fsbl/make_helpers/rsa/core.py

@@ -0,0 +1,53 @@
+#  Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+"""Core mathematical operations.
+
+This is the actual core RSA implementation, which is only defined
+mathematically on integers.
+"""
+
+
+def assert_int(var: int, name: str) -> None:
+    if isinstance(var, int):
+        return
+
+    raise TypeError('%s should be an integer, not %s' % (name, var.__class__))
+
+
+def encrypt_int(message: int, ekey: int, n: int) -> int:
+    """Encrypts a message using encryption key 'ekey', working modulo n"""
+
+    assert_int(message, 'message')
+    assert_int(ekey, 'ekey')
+    assert_int(n, 'n')
+
+    if message < 0:
+        raise ValueError('Only non-negative numbers are supported')
+
+    if message > n:
+        raise OverflowError("The message %i is too long for n=%i" % (message, n))
+
+    return pow(message, ekey, n)
+
+
+def decrypt_int(cyphertext: int, dkey: int, n: int) -> int:
+    """Decrypts a cypher text using the decryption key 'dkey', working modulo n"""
+
+    assert_int(cyphertext, 'cyphertext')
+    assert_int(dkey, 'dkey')
+    assert_int(n, 'n')
+
+    message = pow(cyphertext, dkey, n)
+    return message