I want to encrypt something inside my OS X application: So I thought I'd store
the key inside the keychain.
After a *lot* of reading and tinkering I finally managed to create a new AES
key and get it back out again (as a SecKeyRef).
Now I want to use it with CCCrypt()
That expects raw key data, not a SecKeyRef.
I tried to get the data by asking the keychain for a data blob with
kSecReturnData.
And I do get back a CFDataRef. But it is 96 Bytes, which strikes me as odd for
a 128 bit key. And the actual bytes don't seem to change much between different
keys.
A bit more information:
I create the key using SecKeyGenerateSymmetric() and that seems to work fine as
the key shows up in Keychain Access.
I get the key data out of the keychain using SecItemCopyMatching() which also
seems to work fine. It's just that the data returned is not what I was
expecting. Also, I'm using Swift, and working with C-APIs is quite terrible.
After some research I came up with this code to get at the reference returned
by the SecItemCopyMatching():
var temp: Unmanaged<AnyObject>?
let status = withUnsafeMutablePointer(&temp) {
SecItemCopyMatching(query, UnsafeMutablePointer($0)) }
if status == errSecSuccess {
result = temp!.takeRetainedValue()
}
As I said, that at least seems to work since I get the type of objects expected.
(A lot of seems, I realize. But clearly I'm missing something and I don't know
what.)
So these are my questions:
I found a lot of code online that was promising, but nothing does quite what I
need. Do I even have the right approach here?
Has anyone ever done this? Is there an easier method to get the actual bytes
for an AES key out of a SecKeyRef?
Help! :)
Andreas
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