Document that zipfile decryption is insanely slow and fix a typo and

blatant lie in a docstring (it is not useful for security regardless of
how you spell it).

Doc/library/zipfile.rst

@@ -21,7 +21,8 @@ added to individual archive members---for which see the :ref:`zipinfo-objects`
 documentation). It can handle ZIP files that use the ZIP64 extensions
 (that is ZIP files that are more than 4 GByte in size).  It supports
 decryption of encrypted files in ZIP archives, but it currently cannot
-create an encrypted file.
+create an encrypted file.  Decryption is extremely slow as it is
+implemented in native python rather than C.
 
 For other archive formats, see the :mod:`bz2`, :mod:`gzip`, and
 :mod:`tarfile` modules.

Lib/zipfile.py

@@ -302,7 +302,7 @@ class _ZipDecrypter:
 
     ZIP supports a password-based form of encryption. Even though known
     plaintext attacks have been found against it, it is still useful
-    for low-level securicy.
+    to be able to get data out of such a file.
 
     Usage:
         zd = _ZipDecrypter(mypwd)