Implement optional constant-time decryption flow to hinder Bleichenbacher-like
attacks against RSA- and ElGamal public-key encrypted session keys.
Changes:
- Add `config.constantTimePKCS1Decryption` to enable the constant-time
processing (defaults to `false`). The constant-time option is off by default
since it has measurable performance impact on message decryption, and it is
only helpful in specific application scenarios (more info below).
- Add `config.constantTimePKCS1DecryptionSupportedSymmetricAlgorithms`
(defaults to the AES algorithms). The set of supported ciphers is restricted by
default since the number of algorithms negatively affects performance.
Bleichenbacher-like attacks are of concern for applications where both of the
following conditions are met:
1. new/incoming messages are automatically decrypted (without user
interaction);
2. an attacker can determine how long it takes to decrypt each message (e.g.
due to decryption errors being logged remotely).
- Use PascalCase for classes, with uppercase acronyms.
- Use camelCase for function and variables. First word/acronym is always
lowercase, otherwise acronyms are uppercase.
Also, make the packet classes' `tag` properties `static`.
- `openpgp.generateKey` now expects `userIds` in object format
(strings are no longer supported)
- Remove `util.parseUserId` and `util.formatUserId`
- Replace `UserIDPacket#format` with `UserIDPacket.fromObject`
Also, add a "asStream" parameter to high-level functions to control
whether the return value is a Stream; defaulting to whether the
parameter passed was a Stream.
- Allow leading spaces in headers (since we were already accepting
leading spaces everywhere else in the armored text).
- Read ReadableStreams before passing them to a Worker
