ssb-private-group-keys

Basic helper functions implementing the [private-group] spec.

Currently supports classic & bendy butt feed types.

API

$3

Create a shared key for communication between your feed and _another_ feed.

If you are _encrypting_ a DM, x is your feed, and y is the person you are DM'ing.
If you are _decrypting_ a DM, x is your feed, and y is the message author's.
- NOTE: this is only for the case that the author is someone else, if you're the author, use your own_key

- x_dh_secret, x_dh_public are feed x's diffie-hellman keys
- x_feed_id is the feedId of x
- y_dh_public is feed y's diffie-hellman public key
- y_feed_id is the feedId of y

All inputs are [BFE] style buffers.

The output is a key (buffer) and associated scheme (string) which can be passed into an envelope key_slot

#### directMessageKey.easy(myKeys) => makeKey(feedId) => { key, scheme }

Convenience function which wraps directMessageKey

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$3

If you are _encrypting_ to a P.O. Box, then x is your feed, and y is the P.O. Box.
If you are _decrypting_ a message sent to a P.O. Box, then x is the P.O. Box, and y is the message author's feed.

- x_dh_secret, x_dh_public are x's diffie-hellman keys
- x_id is the BFE id of x
- y_dh_public is y's diffie-hellman public key
- y_id is the BFE id of y

All inputs are [BFE] style buffers.

The output is a key (buffer) and associated scheme (string) which can be passed into an envelope key_slot

#### poBoxKey.easy(myKeys) => makeKey(poboxId) => { key, scheme }

Convenience function which wraps poBoxKey

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$3

Create a secret key that can be used for the group or message key.

methods:
- secretKey.toBuffer() => buffer return raw buffer with the key data in it
- secretKey.toString() => string returns a base64 encoded string of the key

$3

An alternative way to use the constructor, in case you already have the group
key bytes as a buffer, is to pass the buffer as the argument. This simply
"embodies" the group key as a SecretKey instance, it doesn't generate anything
new.

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$3

_alias: DHKeys_

where:
- keys Object (optional)
- is a pair of keys { public, secret? }, each a Buffer or base64 encoded String
- public is required, secret is optional
- if not provided, you are expected to call dhKeys.generate() to generate a keypair
- opts Object (optional)
- opts.fromEd25519 Boolean sets whether the keys are ed25519 signing keys you would like converted to curve25519 encryption keys.
- default: false
- opts.format Integer sets whether the BFE "format" of the encryption key type
- if opts.fromEd25519 = true was used, it's assumed these are dm keys (format = 0)
- else format is not set, which is fine as long as you don't call dhKeys.toBFE()
- dhKeys DiffieHellmanKeys instance with methods:
- dhKeys.generate() => dhKeys - generates public and private dh keys
- dhKeys.toBuffer() => { public: Buffer, secret: Buffer } - returns the raw keys as Buffers
- dhKeys.toBFE() => { public: BFE, secret: BFE } - return [BFE] encodings of the keys (as Buffers)

$3

A class method for creating shared encryption keys.
- A a DHKeys instance, must include secret key
- B a DHKeys instance
- result Buffer the result of the scalarMult
- only useful in advanced cases to conserve memory

NOTE:
- method also takes appropriately shaped objects, see source code.
- there's an advanced signature if you need to conserve memory (A, B, result) => result

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History

This library was originally extracted from [ssb-tribes].

[private-group]: https://github.com/ssbc/private-group-spec
[ssb-tribes]: https://github.com/mixmix/ssb-tribes
[BFE]: https://github.com/ssb-ngi-pointer/ssb-binary-field-encodings-spec