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envelope-js

A javascript tool for cryptographically "boxing" and "unboxing" messages following the envelope spec.

envelope supports encryption to individuals and groups

Example Usage

var { box, unbox, CloakedMsgId } = require('envelope-js')

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API

box(plain_text, feed_id, prev_msg_id, msg_key, recp_keys) => ciphertext

where:

• plain_text Buffer is the content to be "enveloped"
• feed_id Buffer is a type-format-key (TFK) encoded value for the feed authoring a message
• prev_msg_id Buffer is a TFK encoded value of the id of last message of this feeds chain
• msg_key Buffer a randomised 32 Bytes which will be the unique key for this message
• recps_keys Array is a collection of items of form { key, scheme }, where
  • key Buffer is the key the particular recipient
  • scheme String|Buffer is the type of key / the key management scheme for this recipient

unbox(ciphertext, feed_id, prev_msg_id, trial_keys, max_attempts) => plain_text | null

where:

• ciphertext Buffer is envelope
• feed_id Buffer is a type-format-key (TFK) encoded value for the feed authoring a message
• prev_msg_id Buffer is a TFK encoded value of the id of last message of this feeds chain
• trial_keys Array is a collection of items of form { key, scheme }, where
  • key Buffer is the key the particular recipient
  • scheme String|Buffer is the type of key / the key management scheme for this recipient
• max_attempts Integer (default: 8) how many key_slots you want to assume the envelope has
• plain_text Buffer the envelope contents

NOTE: we also expose unboxKey and unboxBody for convenience.

DeriveSecret(feed_id, prev_msg_id) => derive

Used for taking a msg_key (the one-time key for a particular envelope) and deriving other keys used in the envelope (e.g. read_key)

where:

• feed_id Buffer is a TFK encoded id for the feed the envelope is part of
• prev_msg_id Buffer is a TFK encoded id for the message prior to one where our envelope is
  • NOTE if this is the first message, then the K part of prev_msg_id's TFK is a zero-filled Buffer.
• derive(key, labels) => new_key function where:
  • key Buffer is a seed key which we're going to derive from
  • labels Array is a an array of Strings which help define a derivation

new CloakedMsgId(public_msg_id, read_key) => cloakedMsgId

Determine a cloaked message id for a published message following the envelope-spec/cloaked_msg_id/README.md

where:

• public_msg_id Buffer is the id of a enveloped message that's been published (it has an id as it's part of a feed / chain)
• read_key Buffer is the read capability (NOT the msg_key) for this message envelope
• cloakedMsgId is an instance with methods:
  • toBuffer() => Buffer which returns the cloaked id key as a Buffer
  • toString(encoding) => String which returns the cloaked id key as a Buffer (encoding defaults to 'base64')
  • mock() => cloakedMsgId a method for testing. populates the id with random content. if using this, instantiate with no args.

slp.encode(info) => Buffer

where info is an Array of Buffers.

This is "short length-prefixed encoding", see https://github.com/ssbc/envelope-spec/blob/master/encoding/slp.md

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License

MIT