commit 5e7c6dd58a0877cd702f70b509a1ee9781d03cc1
author David Brown <david.brown@linaro.org> Thu Nov 16 14:47:16 2017 -0700
committer David Brown <davidb@davidb.org> Tue Jan 09 09:41:30 2018 -0700
tree c900248756a7a89b45c6e82354aa1395c5a84305
parent d4022576e458f4ced334a045877c22c913638270

imgtool: Update RSA code

Replace RSA code with one using the python 'cryptography' library.  This
library is much more complete, and will make adding support for password
protected keys, and separate public keys easier.

There is, however, a significant change brought about by this change:
the private keys are stored in PKCS#8 format, instead of the raw format
that was used previously.  This is a more modern format that has a few
advantages, including: supporting stronger password protection, and
allowing the key type to be determined upon read.

This tool will still support reading the old style public keys, but
other tools that use these keys will need to be updated in order to work
with the new format.

This new code has some unit tests to go along with it for some basic
sanity testing of the code.

Signed-off-by: David Brown <david.brown@linaro.org>