Simply encrypt and decrypt Strings in Ruby.

encrypt_decrypt.rb

require 'openssl'

class String
  def encrypt(key)
    cipher = OpenSSL::Cipher.new('DES-EDE3-CBC').encrypt
    cipher.key = Digest::SHA1.hexdigest key
    s = cipher.update(self) + cipher.final

    s.unpack('H*')[0].upcase
  end

  def decrypt(key)
    cipher = OpenSSL::Cipher.new('DES-EDE3-CBC').decrypt
    cipher.key = Digest::SHA1.hexdigest key
    s = [self].pack("H*").unpack("C*").pack("c*")

    cipher.update(s) + cipher.final
  end
end


puts plain = 'confidential'           # confidential
puts key = 'secret'                   # secret
puts cipher = plain.encrypt(key)      # 5C6D4C5FAFFCF09F271E01C5A132BE89

puts cipher.decrypt('guess')          # raises OpenSSL::Cipher::CipherError
puts cipher.decrypt(key)              # confidential

@mikosullivan key is used in different context. In this gist, key is a cipher "password". You are trying to set the "encryption key". Consider using your key as cipher password and generate a secure random key. Check out Ruby's documentation for encrypt and key and the section Choosing a key.

If you absolutely need to use passwords as encryption keys, you should use Password-Based Key Derivation Function 2 (PBKDF2) by generating the key with the help of the functionality provided by OpenSSL::PKCS5.pbkdf2_hmac_sha1 or OpenSSL::PKCS5.pbkdf2_hmac.

Although there is #pkcs5_keyivgen, its use is deprecated and it should only be used in legacy applications because it does not use the newer PKCS#5 v2 algorithms.

I suggest, you don't use a password, but generate a secure (random) key. Store it somewhere safe, e.g. base64-encoded.

require 'openssl'
key = 'my-secret-key'
cipher = OpenSSL::Cipher.new('DES-EDE3-CBC')
encrypter = cipher.encrypt
encrypter.key_len
# => 24
encrypter.key = encrypter.random_key

my complete solution is:

require 'openssl'

class String
  def encrypt(key)
    cipher = OpenSSL::Cipher::AES.new(128, :CBC).encrypt
    cipher.key = key
    cipher.update(self) + cipher.final
  end

  def decrypt(key)
    cipher = OpenSSL::Cipher::AES.new(128, :CBC).decrypt
    cipher.key = key
    cipher.update(self) + cipher.final
  end
end

keygen = OpenSSL::Cipher::AES.new(128, :CBC).encrypt
key = keygen.random_key

encrypted = "geheim".encrypt(key)
encrypted.decrypt(key)            # => geheim

avoiding key must be 24 bytes

def encrypt(key)
        cipher = OpenSSL::Cipher.new("aes-256-cbc").encrypt
        cipher.key = Digest::MD5.hexdigest key
        s = cipher.update(self) + cipher.final

        s.unpack('H*')[0].upcase
      end

      def decrypt(key)
        cipher = OpenSSL::Cipher.new('aes-256-cbc').decrypt
        cipher.key = Digest::MD5.hexdigest key
        s = [self].pack("H*").unpack("C*").pack("c*")

        cipher.update(s) + cipher.final
      end

avoiding key must be 24 bytes

def encrypt(key)
        cipher = OpenSSL::Cipher.new("aes-256-cbc").encrypt
        cipher.key = Digest::MD5.hexdigest key
        s = cipher.update(self) + cipher.final

        s.unpack('H*')[0].upcase
      end

      def decrypt(key)
        cipher = OpenSSL::Cipher.new('aes-256-cbc').decrypt
        cipher.key = Digest::MD5.hexdigest key
        s = [self].pack("H*").unpack("C*").pack("c*")

        cipher.update(s) + cipher.final
      end

thanks, works perfectly!