SHA1 skeleton code

hashes/sha1.py

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+"""
+Demonstrates implementation of SHA1 Hash function in a Python class and gives utilities
+to find hash of string or hash of text from a file.
+Usage: python sha1.py --string "Hello World Welcome to Cryptography"
+       pyhton sha1.py --file "hello_world.txt"
+       Without any arguments prints the hash of the string "Hello World"
+Also contains a Test class to verify that the generated Hash is same as that
+returned by the hashlib library
+Reference: https://deadhacker.com/2006/02/21/sha-1-illustrated/
+
+The Algorithm as described in the reference:
+First we start with a message. The message is padded and the length of the message
+is added to the end. It is then split into blocks of 512 bits. The blocks are then
+processed one at a time. Each block must be expanded and compressed.
+The value after each compression is added to a 160bit buffer called the current hash
+state. After the last block is processed the current hash state is returned as
+the final hash.
+"""
+
+import argparse
+import hashlib #hashlib is only used inside the Test class
+
+class SHA1:
+    """
+    Class to contain the entire pipeline for SHA1 Hashing Algorithm
+    """
+    def __init__(self, data):
+        self.data = data
+        self.current_hash = ''
+
+    def padding(self):
+        return
+
+    def split_block(self):
+        return
+
+    def expand_block(self):
+        return
+
+    def compress_block(self):
+        return
+
+    def final_hash(self):
+        assert True #everything done till now
+        # return self.current_hash
+        return hashlib.sha1(bytes(self.data, 'utf-8')).hexdigest()
+
+class SHA1Test:
+    """
+    Test class for the SHA1 class
+    """
+    def __init__(self, data):
+        self.data = data
+
+    def calculated_hash(self):
+        return SHA1(self.data).final_hash()
+
+    def hashlib_hash(self):
+        return hashlib.sha1(self.data.byte_encode()).hexdigest()
+
+    def byte_encode(self):
+        return bytes(self.data, 'utf-8')
+
+    def match_hashes(self):
+        # self.assertEqual(self.calculated_hash(), self.hashlib_hash())
+        return self.calculated_hash() == self.hashlib_hash()
+
+def run_test_case(hash_input = 'Hello World'):
+    """
+    Pulled this out of main because we probably dont want to run the Unit Test
+    each time we want to calculate hash.
+    """
+    print(SHA1Test(hash_input).match_hashes())
+
+
+def main():
+    parser = argparse.ArgumentParser(description='Process some strings or files')
+    parser.add_argument('--string', dest='input_string', default='Hello World',
+                        help='Hash the string')
+    parser.add_argument('--file', dest='input_file', help='Hash contents of a file')
+    args = parser.parse_args()
+    input_string = args.input_string
+    if args.input_file:
+        hash_input = open(args.input_file, 'r').read()
+    else:
+        hash_input = input_string
+    print(SHA1(hash_input).final_hash())
+
+if __name__ == '__main__':
+    main()