by kigster

kigster /sym

Sym is a command line utility and a Ruby API that makes it trivial to encrypt and decrypt sensitive ...

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= symSymmetric Encryption for Humans :toc: :sectnum: :toclevel: 4

==== image:[Gem Version,link=] image:[Build Status,link=] image:[CircleCI,link=] image:[Maintainability,link=]

image:[Coverage,link=""] image:[Gitter,link=] image:[Sym Downloads,link=]

image:[Coverage Map,link=]

Please checkout the following post —[Dead Simple Encryption with Sym] — that announced the initial release of this library, and provides further in-depth discussion. Your donation of absolutely any amount is much appreciated but never required.


== Introduction

NOTE: SYM is an open source command line utility and a Ruby library, which makes it _trivial to encrypt your application secrets with mathematically proven models and ciphers offered in a much larger project — Open SSL.

Unlike many existing encryption tools, sym focuses on narrowing the gap between convenience and security, by offering enhanced usability and a streamlined ruby API and a CLI. The primary goal of the library is to make encryption very easy and transparent. +

  • sym uses the[Symmetric Encryption]_ algorithm. This means that the same key is used to encrypt and decrypt data. In addition to the key, the encryption uses a randomized IV vector, which is automatically generated per each encryption and serialized with the data. Result of encryption is zlib-compressed, and base64 encoded, to be suitable for storage as string. The generated keys are also base64-encoded for convenience. +

  • Finally, the library offers encryption using any regular password, and in particular supports password-protected encryption keys. Automatic key detection algorithm attempts to resolve a provided key as a filename, an environment variable name, an OS-X Keychain password entry name, a key itself, or a default key file. +

NOTE: Sym uses Ruby's

to serialize it's data, and therefore it is not currently possible or easy to deserialize the data in languages other than Ruby.

=== Quick Demo of the CLI in Action


==== Help Screens, Examples and Symit Bash Wrapper

This may be a good time to take a look at the full help message for the

tool, shown naturally with a
option. Examples can be shown with

Additionally, Sym comes with a helpful BASH wrapper


Help screens for

are shown in full on another page -- xref:SYM-CLI.adoc[Sym Help Screens and Symit]. Please refer to it for complete help screens and the examples.

== Supported Ruby Versions

Sym currently builds and runs on the following ruby versions on Travis CI:

.Ruby Version Compatibility [cols="<,<", width="80%"] |=== | MRI Ruby |JRuby

| 2.3.8 | jruby- | 2.4.10| jruby- | 2.5.8 | | 2.6.6 | | 2.7.1 |


=== Motivation

The main goal when writing this tool was to streamline and simplify handling of sensitive data in a trasparent and easy to use way without sacrificing security.

Most common use-cases include:

  • Encrypting/decrypting of application secrets files, so that the encrypted secrets can be safely checked into the git repository and distributed, and yet without much of the added headache that this often requires

  • Secure message transfer between any number of receipients

  • General purpose encryption/decryption with a 256-bit encryption key, optionally itself re-encrypted with a password.

  • General purpose encryption/decryption with an arbitrary password.

Sym is a layer built on top of the[

] library, and, hopefully, makes encryption more accessible to every-day developers, QA, and dev-ops folks, engaged in deploying applications.

=== What's Included

This gem includes two primary components:

. <> with many features to streamline encryption/decryption, and to be integrated into the deployment flow. + . Ruby APIs: ** <> *** is activated by including

module in a class, it adds easy to use
methods. ** <> *** You can instantiate
class with a hash representing CLI arguments, and then call it's
method to mimic CLI execution. ** <> *** This is a convenience class allowing you to encrypt/decrypt files in your ruby code with just couple of lines of code. ** <> *** Use this class to override the default cipher, and configure other parameters such as compression, password caching, and more.

=== Massive Time Savers

Sym tries very hard to get out of your way, to make it feel as if your encrypted files are as easy to work with as the unencrypted files. It accomplishes this transparency with the following features:

  • By using Mac OS-X Keychain,
    offers a simple yet secure way of storing the key on a local machine, much more secure then storing it on a file system.
  • By using a password cache (
    ) via an in-memory provider such as
    invocations take advantage of password cache, and only ask for a password once per a configurable time period.
  • By using
    environment variable
    you can save common flags and they will be applied whenever
    flag is activated.
  • By reading a key from the default key source file
    which requires no flags at all.
  • By utilizing the
    option to quickly encrypt a regular file
    , or decrypt an encrypted file with extension
  • By using the
    -t file
    (edit) mode
    , that opens an encrypted file in your
    , and replaces the encrypted version upon save & exit.

As you can see, we really tried to build a tool that provides good security for application secrets, including password-based encryption, but does not annoyingly ask for password every time. With

option, and
options you can treat encrypted files like regular files.

[quote, Socrates (LOL)]

Encrypting application secrets had never been easier!

== Using Sym

[discrete] ==== Installation

If you plan on using the library in your Ruby project with Bundler managing its dependencies, just include the following line in your


gem 'sym'

And then run


Or install it into the global namespace with

gem install


$ gem install sym $ sym -h

$ sym -E # see examples

BASH Completion

Optionally, after gem installation, you can also install bash-completion of gem's command line options, but running the following command (and feel free to use any of the "dot" files you prefer):

sym -B ~/.bashrc

Should you choose to install it (this part is optional), you will be able to use "tab-tab" after typing

, and you'll be able to choose from all of the supported flags.

[discrete] ==== Typical Use-Case Scenario

. You generate a new encryption key, that will be used to both encrypt and decrypt the data. The key is 256 bits, or 32 bytes, or 45 bytes when base64-encoded, and can be generated with

sym -g
. The key must be saved somewhere for later retrieval. The key should not be easily accessible to an attacker. Note, that while generating the key, you can: ** optionally password protect the key with
sym -gp
** save the key into a file with
sym -gpo key-file
** save it into the OS-X Keychain, with
sym -gpx keychain-name
** cache the password, with
sym -gpcx keychain-name
** Normally,
will print the resulting key to STDOUT ** You can prevent the key from being printed to STDOUT with
. . Next, let's assume you have a file or a string that you want to encrypt. We call this data. . In order to encrypt the data, we must supply an encryption key. Flag
automatically retrieves the key, by trying to read it in several distinct ways, such as: ** a file with a pathname specified by the argument (eg,
-k ~/.key
) ** or environment variable (eg
) ** or OS-X Keychain entry ** verbatum string argument (not recommended) ** alternatively, you can paste the key interactively with
or save the default key in
file. . Finally, we are ready to encrypt. The data to be encrypted can be read from a file with
-f filename
, or it can be read from STDIN, or a passed on the command line with
-s string
. For example,
sym -e -k ~/.key -f /etc/passwd
will encrypt the file and print the encrypted contents to STDOUT. . Instead of printing to STDOUT, the output can be saved to a file with
or a simple redirect or a pipe. . Encrypted file can later be decrypted with
+sym -d ...+
assuming the same key it was encrypted with. . Encrypted file with extension
can be automatically decrypted with
-n/--negate file
option; if the file does not end with
, it is encrypted and
extension added to the resulting file. . With
-t/--edit file
flag you can edit an encrypted file in VIM (or
) any encrypted file and edit it. Once you save it, the file gets re-encrypted and replaces the previous version. A backup can be created with
option. See the section on <>

A sample session that uses Mac OS-X Keychain to store the password-protected key.


Gen a new key, password-encrypt it, cache the password, save

result in the key chain entry 'my-new-key' (but don't print it '-q')

❯ sym -gpqcx my-new-key New Password : ••••••••• Confirm Password : •••••••••

❯ sym -eck my-new-key -s 'My secret data' -o secret.enc Password: •••••••••

❯ cat secret.enc BAhTOh1TeW06OkRhdGE6OldyYXBFefDFFD.....

❯ sym -dck my-new-key -f secret.enc My secret data

Now, let's save our keychain key in the default key file:

❯ sym -ck my-new-key -o ~/.sym.key

Now we can decrypt/encrypt with this key at will

❯ sym -n secret.enc

created a decrypted file

Lets now save common flags in the SYM_ARGS bash variable:

❯ export SYM_ARGS="-ck my-new-key"

To have sym parse the SYM_ARGS variable, we must activate this feature with -A

❯ sym -Adf secret.enc

My secret data

Note that password caching is off by default, but is enabled with

flag. In the example above, the decryption step fetched the password from the cache, and so the user was not required to re-enter the password.


[discrete] ==== Inline Editing of Encrypted Files


CLI tool supports one particularly interesting mode, that streamlines handling of encrypted files. The mode is called edit mode, and is activated with the

Instead of decrypting data anytime you need to change it into a new file and then manually re-encrypting the result, you can use the shortcut flag

(for "edit"), which decrypts your data into a temporary file, automatically opening it with an

sym -t config/application/secrets.yml.enc -k ~/.key

This is one of those time-saving features that can make a difference in making encryption feel easy and transparent.

NOTE: this mode does not seem to work with GUI editors such as Atom or TextMate. Since

waits for the editor process to complete, GUI editors "complete" immediately upon starting a windowed application.

In this mode several flags are of importance:

-b (--backup) – will create a backup of the original file -v (--verbose) - will show additional info about file sizes

Here is a full command that opens a file specified by

-f | --file
, using the key specified in
-k | --keyfile
, in the editor defined by the
environment variable (or if not set -- defaults to

Example: here we edit an encrypted file in

, while using interactive mode to paste the key (
-i | --interactive
), and then creating a backup file (
-b | --backup
) upon save:

sym -ibt data.enc # => Private Key: •••••••••••••••••••••••••••••••••••••••••••• # # => Diff: # 3c3 # # (c) 2015 Konstantin Gredeskoul. All rights reserved. # --- # # (c) 2016 Konstantin Gredeskoul. All rights reserved.

Note the

shown after save.

==== CLI Help Reference

image::design/sym-help.png[Sym Help,width=651]


== Ruby API

=== Including


Low-level encryption routines can be imported by including

module into your class or a module. Such class will be decorated with new class methods
, as well as instance methods
, and

==== Class Method


This method will generate a new key each time it's called.

==== Class Method

#private_key(value = nil)

This method will either assign an existing key (if a value is passed) or generate and save a new key in the class instance variable. Therefore each class including

will (by default) use a unique key (unless the key is passed in as an argument).

The following example illustrates this point:


require 'sym'

class TestClass include Sym end

@key = TestClass.createprivatekey @key.eql?(TestClass.private_key) # => false

A new key was created and saved in #private_key accessor.

class SomeClass include Sym privatekey TestClass.privatekey end

@key.eql?(SomeClass.private_key) # => true (it was assigned)

==== Encrypting and Decrypting

So how would we use this library from another Ruby project to encrypt and decrypt values?

After including the

module, two instance methods are added:
  • #encr(value, private_key)
  • #decr(value, private_key)

Therefore you could write something like this below, protecting a sensitive string using a class-level secret.


require 'sym' class TestClass include Sym private_key ENV['SECRET']

def sensitivevalue=(value) @sensitivevalue = encr(value, self.class.privatekey) end def sensitivevalue decr(@sensitivevalue, self.class.privatekey) end


==== Encrypting the Key Itself

You can encrypt the private key using a custom password. This is highly recommended, because without the password the key is the only piece that stands between an attacker and decrypting your sensitive data.

For this purpose, two more instance methods exist:

  • #encr_password(data, password, iv = nil)
  • #decr_password(encrypted_data, password, iv = nil)

They can be used independently of

to encrypt/decrypt any data with a password.


=== Using

API for Reading/Writing Encrypted/Decrypted data

This is probably the easiest way to leverage Sym-encrypted files in your application -- by loading them into memory with

. This class provides a very simple API while supporting all of the convenience features of the rich application API (see below).

You instantiate

with just two parameters: a
to a file (encrypted or not), and the
identifier. The identifier can either be a filename, or OS-X Keychain entry, or environment variable name, etc -- basically it is resolve like any other
CLI flag.

The following methods are available:

  • #encrypt
    -- returns an encrypted string representing the encrypted contents ofa file specified by the pathname.
  • #decrypt
    -- returns a decrypted string representing the decrypted contents of a file specified by the pathname.
  • #encrypt_to(filename)
    -- encrypts the contents of a file specified by the pathname, and writes the result to a
  • #decrypt_to(filename)
    -- decrypts the contents of a file specified by the pathname, and writes the result to a

==== Example: Using

with the
) gem

In this example, we assume that the environment variable

contain the key to be used in decryption.


require 'sym/magicfile' require 'yaml' secrets ='/usr/local/etc/secrets.yml.enc', 'PRIVATEKEY')

hash = YAML.load(secrets.decrypt)

Let's say that you are using[RailsConfig] gem for managing your Rails application setings. Since the gem allows appending settings from a hash, you can simply do the following in your

, and after all of the unencrypted settings are loaded:


require 'config' require 'sym/magicfile' require 'yaml' Settings.addsource!( YAML.load( '/usr/local/etc/secrets.yml.enc', 'PRIVATE_KEY' ).decrypt) )



=== Using


Since the command line interface offers much more than just encryption/decryption of data with a key, majority of these features are available through


The class is instantiated with a hash that would be otherwise generated by parsing CLI arguments, typical

. For example, to generate the key, pass
generate: true
-- essentially any flag in it's long form can be converted into a hash member.

Here is an example:


require 'sym/application'

key = true).execute

=> '75ngenJpB6zL47/8Wo7Ne6JN1pnOsqNEcIqblItpfg4='

=== Ruby API Conclusion


's rich ruby API you can perform both low-level encryption/decryption, as well as high-level management of encrypted files. By using
classes you can access the entire set of functionality expressed vi the CLI, described in details below.


== Using

with the Command Line

=== Encryption Keys

The private key is the cornerstone of the symmetric encryption. Using

, the key can be:
  • generated and printed to STDOUT, or saved to Mac OS-X KeyChain or a file
  • fetched from the Keychain in subsequent operations
  • password-protected during generation (or import) with the
  • password can be cached using a locally running
    , assuming the
    flag is provided.
  • must be kept very well protected and secure from attackers.

The unencrypted private key will be in the form of a base64-encoded string, 45 characters long.

Encrypted (with password) private key will be considerably longer, perhaps 200-300 characters long.

==== Generating the Key -- Examples


Let's generate a new key, and copy it to the clipboard (using
command on Mac OS-X):

$ sym -g | pbcopy

Or save a new key into a bash variable

$ KEY=$(sym -g)

Or save it to a file:

$ sym -go ~/.key

Or create a password-protected key (
), and save it to a file (

cache the password (
), and don't print the new key to STDOUT (
for quiet)

$ sym -gpcqo ~/.secret New Password: •••••••••• Confirm Password: ••••••••••


==== Resolving the


You can use the generated private key by passing an argument to the


Sym attempts to automatically resolve the key source by trying each of the following options, and then moving on to the next until the key is found, or error is shown:

. the

-k value
flag, where the value is one of: ** a file path, eg (
-k ~/.key
) ** an environment variable name (
) ** an actual base64-encoded key (not recommended for security reasons) ** a keychain name (
-k keychain-entry-name
) . pasting or typing the key with the
(interactive) flag . if exists, a default key file, located in your home folder:
is used only when no other key-specifying flags were passed in.

==== Encryption and Decryption


==== Inline Editing


CLI tool supports one particularly interesting mode, that streamlines handling of encrypted files. The mode is called edit mode, and is activated with the
-t file

In this mode

will automaticaly decrypt the encrypted file into a temporary file, and then open it in
. Once you quit the editor,
will automatically diff the new and old content, and if it is different,
will re-encrypt the new contents and overwrite the original file. You can create an optional backup by adding

NOTE: this mode does not seem to work with GUI editors such as Atom or TextMate. Since

waits for the editor process to complete, GUI editors "complete" immediately upon starting a windowed application. In this mode several flags are of importance:

-b (--backup) – will create a backup of the original file -v (--verbose) - will show additional info about file sizes

Here is a full command that opens a file specified by

-t | --edit file
, using the key specified in
-k | --keyfile
, in the editor defined by the
environment variable (or if not set -- defaults to

To edit an encrypted file in

, while asking to paste the key (
-i | --interactive
), while creating a backup file (
-b | --backup


sym -tibf data.enc # => Private Key: •••••••••••••••••••••••••••••••••••••••••••• # # => Diff: # 3c3 # # (c) 2015 Konstantin Gredeskoul. All rights reserved. # ---

# # (c) 2016 Konstantin Gredeskoul. All rights reserved.

==== Using KeyChain Access on Mac OS-X

KeyChain storage is a huge time saver. It allows you to securely store the key the keychain, meaning the key can not be easily extracted by an attacker without a login to your account. Just having access to the disk is not enough.

Apple had released a

command line tool, which this library uses to securely store a key/value pair of the key name and the actual private key in your OS-X KeyChain. The advantages of this method are numerous:
  • The private key won't be lying around your file system unencrypted, so if your Mac is ever stolen, you don't need to worry about the keys running wild.
  • If you sync your keychain with the iCloud you will have access to it on other machines

As mentioned previously, to add the key to the KeyChain on the Mac, use

flag with
flag when generating a key. The
key name
is what you call this particular key, based on how you plan to use it. For example, you may call it
, etc.

The following command generates the private key and immediately stores it in the KeyChain access under the name provided:

sym -gx staging # the key is passwordless sym -gpcx staging # this key is password protected, with the password cached

Next, whenever you need to use this key, you can specify the key with

-k staging

Finally, you can delete a key from KeyChain access by running:

keychain delete

Below we describe the purpose of the executable

shipped with sym.

==== KeyChain Key Management

is an additional executable installed with the gem, which can be used to read (find), update (add), and delete keychain entries used by

It's help message is self-explanatory:

Usage: keychain [ add | find | delete ]

==== Moving a Key to the Keychain

You can easily move an existing key from a file or a string to a keychain by combining -k or -k to read the key, with -x to write it.

sym -k $keysource -x mykey

==== Adding Password to Existing Key

You can add a password to a key by combining one of the key description flags (-k, -i) and then also -p. Use

to hide new key from the STDOUT, and
to cache the password.

sym -k $mykey -pqcx moo

The above example will take an unencrypted key passed in

, ask for a password and save password protected key into the keychain with name "moo."

==== Password Caching

Nobody likes to re-type passwords over and over again, and for this reason Sym supports password caching via a locally running

instance (using the default port 11211, if available).

Multiple Providers

Cache is written using the Provider design pattern (a.k.a. plugin architecture), and so it's easy to add a new Cache Provider that uses a custom backend. The supplied production-ready provider only works with a

daemon running (ideally) locally.

For customization of memcached location, we refer you to the

class for an example of how to configure MemCached provider -- shown below in the Ruby API section.

In order to control password caching, the following flags are available:

  • -c
    turns on caching
  • -u seconds
    sets the expiration for cached passwords
  • -r memcached
    controls which of the providers is used. Without this flag, sym auto-detects caching provider by first checking for

==== Saving Common Flags in an Environment Variable

You can optionally store frequently used flags for

in the
environment variable. For example, to always cache passwords, and to always use the same encryption key from the keychain named "production", set the following in your

export SYM_ARGS="-cx production"

This will be automatically appended to the command line if the

flag is provided, and so to encrypt/decrypt anything with password caching enabled and using that particular key, you would simply type:


-cx production are added from SYM_ARGS

sym -Aef file -o file.enc

And to decrypt:

sym -Adf file.enc -o file.original

Or edit the encrypted file:

sym -Atf file.enc

== Fine Tuning


=== Configuration

The library contains a

singleton class, which can be used to tweak some of the internals of the gem. Its meant for advanced users who know what they are doing. The code snippet shown below is an actual default configuration. You can override the defaults by including a similar snipped in your application initialization, right after the
require 'sym'
. The
class is a Singleton, so changes to it will propagate to any subsequent calls to the gem.


require 'zlib' require 'sym' Sym::Configuration.configure do |config| config.passwordcipher = 'AES-128-CBC' config.datacipher = 'AES-256-CBC' config.privatekeycipher = config.datacipher config.compressionenabled = true config.compressionlevel = Zlib::BESTCOMPRESSION config.encryptedfileextension = 'enc' config.defaultkeyfile = "#{ENV['HOME']}/.sym.key"

config.passwordcachetimeout = 300

# When nil is selected, providers are auto-detected. config.passwordcachedefaultprovider = nil config.passwordcachearguments = { # In-memory password cache configuration: # Memcached Provider – local is the default, but can be changed. memcached: { args: %w(, opts: { namespace: 'sym', compress: true, expiresin: config.passwordcachetimeout } } }


As you can see, it's possible to change the default cipher type, although not all ciphers will be code-compatible with the current algorithm, and may require additional code changes.

==== Encryption Features & Cipher


executable as well as the Ruby API provide:
  • Symmetric data encryption with: ** the Cipher
    used by the US Government ** 256-bit private key, that *** can be generated and is a base64-encoded string about 45 characters long. The decoded key is always 32 characters (or 256 bytes) long. *** can be optionally password-encrypted using the 128-bit key, and then be automatically detected (and password requested) when the key is used *** can optionally have its password cached for 15 minutes locally on the machine using
  • Rich command line interface with some innovative features, such as inline editing of an encrypted file, using your favorite
  • Data handling: ** Automatic compression of the data upon encryption ** Automatic base64 encryption to make all encrypted strings fit onto a single line. ** This makes the format suitable for YAML or JSON configuration files, where only the values are encrypted.
  • Rich Ruby API
  • (OS-X Only): Ability to create, add and delete generic password entries from the Mac OS-X KeyChain, and to leverage the KeyChain to store sensitive private keys.

== Development

After checking out the repo, run

to install dependencies. Then, run
rake spec
to run the tests. You can also run
for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run

bundle exec rake install

To release a new version, update the version number in

, and then run
bundle exec rake release
, which will create a git tag for the version, push git commits and tags, and push the
file to[].

[discrete] ==== Contributing

Bug reports and pull requests are welcome on GitHub at

===== UML

Here are a couple of UML diagrams depicting the current, and possibly future state of the codebase.


===== Current Design

image::design/sym-class-dependency-vertical.png[UML Vertical]


===== Future Design

image::design/sym-class-dependency-future-refactor.png[UML Refactor]

=== License

Sym library is © 2016-2020 Konstantin Gredeskoul and Contributors.

The gem is available as open source under the terms of the[MIT License]. The library is designed to be a layer on top of[

], distributed under the[Apache Style license].

=== Acknowledgements

  • The blog post[(Symmetric) Encryption With Ruby (and Rails)] provided the inspiration for this gem.
  • We'd like to thank[Spike Ilacqua], the author of the[strongbox] gem, for providing very easy-to-read code examples of symmetric encryption.
  • We'd like to thank[Wissam Jarjoui] for support and inspiration, as well as testing of the early versions of this gem.

==== Contributors:

Contributions of any kind are very much welcome from anyone.

Any pull requests will be reviewed promptly.

Please submit feature requests, bugs, or donations :)

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