git hook to test if a file contains the right data

Question

I have a git repo with key files that have to be all in the format

#possible comment
key "<key with 64 chars>"; # possible comment
vpn .... #optional line

I would like to add a hook into our git repository, that when you try to commit a new file, this regular expression is checked on all files in the repository beforehand:

cat *|grep -v -E "^\s*key\s+\"[0-9a-f]{64}\";\s*(#.*)*$"|grep -v -E "(^#|vpn|^$)"

I created a .git/hooks/pre-commit file:

#!/bin/sh

if git rev-parse --verify HEAD >/dev/null 2>&1
then
    against=HEAD
else
    # Initial commit: diff against an empty tree object
    against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

# Redirect output to stderr.
exec 1>&2

diffstr=$(git diff --cached $against | sed 's/^+//g' | grep -E "^\+[^\+]" \
| grep -v -E "^key \"\w{64}\";\s*(#.*)*$" | grep -v -E "(^#|vpn|^$)")
if [ "$diffstr" != "" ] ; then
    echo "You have a malformed key in your changes, you can't commit until it has been corrected:"
    echo $diffstr
    exit 1
fi

I want to be stopped from committing changed/new key-files that are not in the correct format. Any of the following:

• don't start with key
• dont use "-quotes
• dont end with ; (optionally followed by a comment)
• where the key is not a 64 hex characters.
• any other lines, that don't start with comment #

But my solution still doesn't stop me from committing wrong key files. What am I doing wrong?