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CryptoRuby 101
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Zoran Majstorovic
April 28, 2015
Programming
1
280
CryptoRuby 101
basic stuff in general cryptography (encrypt/decrypt) using Ruby OpenSSL Extension
Zoran Majstorovic
April 28, 2015
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Transcript
CryptoRuby 101 by
[email protected]
from A Professional Mobile Device Management
Company
CryptoRuby 101 very basic stuff in general cryptography (encypt/decript) featuring
Ruby Standard Library Extension (OpenSSL) what to expect from today's
(en|de)crypt symmetric encrypt with secret key decrypt with secret key
asymmetric ecrypt with public key decrypt with private key
• an open-source library, written in C • implements basic
cryptographic functions and SSL and TLS protocols • founded in 1998, used by 2/3 of all webservers • https://www.openssl.org
require 'openssl' • Ruby Standard Library Extension: /ext/openssl/* • http://ruby-doc.org/stdlib-2.2.2/libdoc/openssl/rdoc/index.html
symmetric-key cryptography a cipher (or cypher) is an algorithm
for encryption or decryption OpenSSL::Cipher Chiper Block Chaining mode encryption
CBC = Chiper Block Chaining CBC mode encryption
CBC = Chiper Block Chaining CBC mode encryption
source: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation CBC mode encryption
OpenSSL::Cipher Code Snippet
msg = 'hello secret world' cipher = OpenSSL::Cipher.new('AES-256-CBC').encrypt iv =
cipher.random_iv key = cipher.random_key encrypted = cipher.update(msg) + cipher.final # safe to share publicly: encrypted, alg, iv decipher = OpenSSL::Cipher.new('AES-256-CBC').decrypt dechiper.iv, dechiper.key = iv, key decrypted = decipher.update(encrypted) + decipher.final puts msg == decrypted #=> true
ActiveSupport::MessageEncryptor a simple way to encrypt values which get
stored somewhere you don't trust
ActiveSupport::MessageEncryptor #encrypt_and_sign #decrypt_and_verify • implemented using OpenSSL::Cipher • https://github.com/rails/rails/blob/master/activesupport/ lib/active_support/message_encryptor.rb#L100
• default cipher algorythm is 'AES-256-CBC'
ActiveSupport::MessageEncryptor class EncryptedCookieJar def initialize(parent_jar, key_generator, options = {}) @parent_jar
= parent_jar @options = options secret = key_generator.generate_key(@options[:encrypted_cookie_salt]) sign_secret = key_generator.generate_key(@options[:encrypted_signed_cookie_salt]) @encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, digest: digest, ...) end # etc... used as @encryptor in ActionDispatch::EncryptedCookieJar https://github.com/rails/rails/blob/master/actionpack/lib/action_dispatch/ middleware/cookies.rb
ActiveSupport::MessageEncryptor Code Snippet
cookie = "user_id:1" key = Rails.application.secrets[:secret_key_base] chiper = ActiveSupport::MessageEncryptor.new(key) encrypted_cookie
= chiper.encrypt_and_sign(cookie) # cookie: "#{base64_encrypted_data}--#{base_64_iv}" # read encrypted_cookie decrypted = chiper.decrypt_and_verify(encrypted_cookie) cookie == decrypted #=> true
cookie = "user_id:1" salt = SecureRandom.random_bytes(64) pass = 'password' key
= ActiveSupport::KeyGenerator.new(pass).generate_key(salt) chiper = ActiveSupport::MessageEncryptor.new(key) encrypted_cookie = chiper.encrypt_and_sign(cookie) # cookie: "#{base64_encrypted_data}--#{base_64_iv}" # read encrypted_cookie decrypted = chiper.decrypt_and_verify(encrypted_cookie) cookie == decrypted #=> true
Re-cap • explore OpenSSL namespace http://ruby-doc.org/stdlib-2.2.2/libdoc/openssl/rdoc/index.html • start with simple
OpenSSL::Cipher http://ruby-doc.org/stdlib-2.2.2/libdoc/openssl/rdoc/OpenSSL/Cipher.html • dive into Asymmetric Public Key Algorithms: OpenSSL::PKey http://ruby-doc.org/stdlib-2.2.2/libdoc/openssl/rdoc/OpenSSL/PKey.html http://ruby-doc.org/stdlib-2.2.2/libdoc/openssl/rdoc/OpenSSL/PKey/RSA.html
Gems • ActiveSupport • SymmetricEncryption provides encryption of data for
Ruby and Rails: https://github.com/reidmorrison/symmetric-encryption • Strongbox provides Public Key Encryption for ActiveRecord: https://github.com/spikex/strongbox • etc: https://www.ruby-toolbox.com/categories/encryption
cryptofails.com “Be skeptical of everything you read and hear about
crypto”