Where is the Keychain lock icon located? By using Google and Co. and the built-in terminal command locate, I already found the following icons: 

/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/UnlockedIcon.icns
/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/LockedIcon.icns

But their resolution is not very high. 

I am looking for the icon that is displayed every time one has to authenticate (f.ex. when unlocking the keychain): 



I think it exists without the little keys. I cannot find it under /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/. 

Do you know where this icon is hidden? Thanks a lot!

Related to this post: Where is the icon used in this dialogue box?
Apple doesn’t store all icons anymore for compound items and overlays the key icon over the lock icon in this case. The same with the finder icon over the lock. 

Here are the two sources:

Lock Icon

The lock icon is located in 

/System/Library/CoreServices/SystemAppearance.bundle/Contents/Resources/Assets.car



Install Theme Engine

Note: You may want to download the released version.
Open the file
Select Security
Drag the icon to the desktop to convert to a png




Keychain Icon

macOS just places the app icon in front of it.  In this case the KeyChain icon is in 

/Applications/Utilities/Keychain Access.app/Contents/Resources/AppIcon.icns