postgres version

server/spam.py

@@ -0,0 +1,37 @@
+def generate_spam_flag():
+    import base64, hashlib, os, re
+    encode = lambda s: re.sub(r'[a-z/+=\n]', r'', base64.encodebytes(s).decode()).upper()
+    secret = '1234'
+
+    prefix = encode(os.urandom(64))[:16]
+    suffix = encode(hashlib.sha256((prefix + secret).encode()).digest())[:15]
+    return prefix + suffix + '='
+
+
+def is_spam_flag(flag):
+    import base64, hashlib, re
+    encode = lambda s: re.sub(r'[a-z/+=\n]', r'', base64.encodebytes(s).decode()).upper()
+    secret = '1234'
+
+    prefix = flag[:16].upper()
+    suffix = encode(hashlib.sha256((prefix + secret).encode()).digest())[:15]
+    return flag[16:].upper() == suffix + '='
+
+
+def test():
+    import base64, hashlib, os, re
+    encode = lambda s: re.sub(r'[a-z/+=\n]', r'', base64.encodebytes(s).decode()).upper()
+    for i in range(10**4):
+        flag = encode(os.urandom(128))[:31] + '='
+        if i < 30:
+            print(flag)
+        assert not is_spam_flag(flag)
+
+    for i in range(10**3):
+        assert is_spam_flag(generate_spam_flag())
+
+    print('Ok')
+
+
+if __name__ == '__main__':
+    test()