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Secure container.





Build Status


npm i --save secure-container


Main Module

This is the main module most users should use; other modules are for advanced users only.

import * as seco from 'secure-container'
// OR
const seco = require('secure-container')


encrypt(data, options)

  • data (String | Buffer) Data to encrypt
  • options (Object)
    • header (Object)
      • appName (String) Name of your app
      • appVersion (String) Version of your app
    • passphrase (String | Buffer) Passphrase used to encrypt the data
    • metadata (Object)
    • blobKey (Buffer)

Note: Must set either passphrase or metadata & blobKey.

Returns an Object that contains:

  • encryptedData (Buffer) The encrypted data
  • blobKey (Buffer)
  • metadata (Object)


decrypt(encryptedData, passphrase)

  • encryptedData (Buffer) Data to decrypt
  • passphrase (String | Buffer) Passphrase to decrypt the data

Returns an Object that contains:

  • data (Buffer) The file data
  • header (Object) The header for the secure-container
  • blobKey (Buffer)
  • metadata (Object)

header module

import * as header from 'secure-container/lib/header'
// OR
const header = require('secure-container/lib/header')


Create a header object.

  • data (Object)
    • appName (String) Name of your app
    • appVersion (String) Version of your app

Returns an Object.


Serialize a header object. headerObj is a header object made with create(). Returns a Buffer.


Decodes a header buffer and returns the Object.

metadata module

import * as metadata from 'secure-container/lib/metadata'
// OR
const metadata = require('secure-container/lib/metadata')


Create a metadata object. Returns an Object.

metadata.encryptBlobKey(metadata, passphrase, blobKey)

  • metadata (Object) Metadata created with metadata.create().
  • passphrase (String | Buffer)
  • blobKey (Buffer)

Mutates metadata object; returns undefined.


Serialize a metadata object. Returns a Buffer.


Takes a metadata buffer, decodes it, and returns an object.

metadata.decryptBlobKey(metadata, passphrase)

  • metadata (Object) Metadata with an encrypted blobKey.
  • passphrase (String | Buffer)

Returns blobKey as a buffer.

blob module

import * as blob from 'secure-container/lib/blob'
// OR
const blob = require('secure-container/lib/blob')

blob.encrypt(data, metadata, blobKey)

  • data (Buffer) Data or message to encrypt.
  • metadata (Object) Metadata object.
  • blobKey (Buffer)

Mutates metadata. Returns an object:

  • blob (Buffer) Encrypted data.
  • blobKey (Buffer) The blobKey you passed in.

blob.decrypt(blob, metadata, blobKey)

  • blob (Buffer) Encrypted data.
  • metadata (Object) Metadata object.
  • blobKey (Buffer)

Returns the decrypted data as a buffer.

file module

import * as file from 'secure-container/lib/file'
// OR
const file = require('secure-container/lib/file')

file.computeChecksum(metadata, blob)

  • metadata (Buffer) Metadata as a Buffer
  • blob (Buffer) Encrypted blob

Returns a sha256 checksum as a buffer.


  • fileObj (Object)
    • header (Buffer) Serialized header
    • checksum (Buffer) Checksum from file.computeChecksum()
    • metadata (Buffer) Metadata as a Buffer
    • blob (Buffer) Encrypted blob

Returns a buffer.


The opposite of file.encode(). Takes a buffer and returns an object.

File Format Description

This is the documentation for the binary structure of secure containers.

For clarity, we have split the documentation into four sections: header, checksum, metadata, and blob.


Size | Label | Description | ---- | ----- | ----------- | 4 | magic | The magic header indicating the file type. Always SECO. 4 | version | File format version. Currently 0, stored as UInt32BE. 4 | reserved | Reserved for future use. 1 | versionTagLength | Length of versionTag as UInt8. versionTagLength | versionTag | Should be 'seco-v0-scrypt-aes'. 1 | appNameLength | Length of appName as UInt8. appNameLength | appName | Name of the application writing the file. 1 | appVersionLength | Length of appVersion as UInt8. appVersionLength | appVersion | Version of the application writing the file.


32-byte sha256 checksum of the following data:

  1. The metadata.
  2. Byte-length of the blob, stored as UInt32BE.
  3. The blob.


Size | Label | Description | ---- | ----- | ----------- | 32 | salt | Scrypt salt. 4 | n | Scrypt n parameter. 4 | r | Scrypt r parameter. 4 | p | Scrypt p parameter. 32 | cipher | Currently aes-256-gcm stored as a zero-terminated C-string. 12 | iv | blobKey's iv. 16 | authTag | blobKey's authTag. 32 | key | blobKey's key. 12 | iv | The blob's iv. 16 | authTag | The blob's authTag.


Size | Label | Description | ---- | ----- | ----------- | 4 | blobLength | Length of blob as UInt32BE. blobLength | blob | Encrypted data.