Envelope Format

Version 0

Field	Size	Offset	Description
Version	1	0	Version of the pigi file format. This defines the rest of the fields
Algorithm	1	1	A single-byte to signal which algorithms are used
File ID	32	2	The SHA256 of the original file
Length	4	34	The length of the Payload field (uint32 big endian)
IV	16	38	The Initialization Vector
Payload	Value(Length)	54	The encrypted and compressed payload

The Pigi file format version 0 can be defined using the restructure Node.js library as follows:

import r from 'restructure';

export const PigiStruct = new r.VersionedStruct(r.uint8, {
  0: {
    algorithm: new r.Enum(r.uint8, Algorithms),
    originalFileHash: new r.Buffer(32),
    encryptedSize: r.uint32be,
    iv: new r.Buffer(16),
    encryptedData: new r.Buffer('encryptedSize'),
  },
});