In the lightweight build, lazily load bn.js only when necessary.
Also, use Uint8Arrays instead of strings in PKCS1 padding functions, and
check that the leading zero is present when decoding EME-PKCS1 padding.
Also, when generating RSA keys in JS, generate them with p < q, as per
the spec.
Also, when generating RSA keys using Web Crypto or Node crypto, swap the
generated p and q around, so that will satisfy p < q in most browsers
(but not old Microsoft Edge, 50% of the time) and so that we can use the
generated u coefficient (p^-1 mod q in OpenPGP, q^-1 mod p in RFC3447).
Then, when signing and verifying, swap p and q again, so that the key
hopefully satisfies Safari's requirement that p > q, and so that we can
keep using u again.
This PR adds four config options to configure whether and how to load
indutny/elliptic: use_indutny_elliptic, external_indutny_elliptic,
indutny_elliptic_path and indutny_elliptic_fetch_options.
Also:
- Use tweetnacl.js instead of indutny/elliptic for curve25519 key generation
- Don't initialize indutny's curve25519, improving performance when using that curve
- Verify NIST signatures using Web Crypto instead of indutny/elliptic when not streaming
- Move KeyPair.sign/verify to ecdsa.js
- Move KeyPair.derive to ecdh.js
- Move keyFromPrivate and keyFromPublic to a new indutnyKey.js file
