Extend and improve the importing and exporting of keys.#52

Merged

mpdavis merged 8 commits intompdavis:masterfrom

TobiasKappe:pullreq-serialization-deserialization

Jun 6, 2017

Commits on May 13, 2017

Use secp256r1 key in EC test rather than secp256k1 key.
TobiasKappe
committed
Serialization of keys to dictionary corresponding to their JWK representation.
TobiasKappe
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Support reading in private keys from a dictionary.
TobiasKappe
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Commits on May 14, 2017

Commits on May 16, 2017

Translate errors raised by cryptography when signing with EC to JWKErrors.
TobiasKappe
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Parametrize tests of backends whenever possible.
TobiasKappe
committed