First I have to say that don't really see any reason for this. The double entering of values is a service to the user to help verify that the data is correctly entered. If the users don't want this help, they can circumvent it on their own risk. It might feel awkward for the user to enter the same data twice, but it's all for their benefit. If you try to force them to use this feature, it will feel even more awkward. I think that it's more effective to try to educate the users of the reason for this feature, instead of forcing it upon them. It might be possible to prohibit copying and pasting, but it's not that easy to make it work in all browsers, as it's not really a browser function but rather a system function. There is no simple setting that allows you to control copying and pasting in a field.
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