class RbNaCl::SimpleBox
The simplest nonce strategy that could possibly work
This class implements the simplest possible nonce generation strategy to wrap a RbNaCl::Box or RbNaCl::SecretBox. A 24-byte random nonce is used for the encryption and is prepended to the message. When it is time to open the box, the message is split into nonce and ciphertext, and then the box is decrypted.
Thanks to the size of the nonce, the chance of a collision is negligible. For example, after encrypting 2^64 messages, the odds of their having been repeated nonce is approximately 2^-64. As an additional convenience, the ciphertexts may be encoded or decoded by any of the encoders implemented in the library.
The resulting ciphertexts are 40 bytes longer than the plain text (24 byte nonce plus a 16 byte authenticator). This might be annoying if you're encrypting tweets, but for files represents a fairly small overhead.
Some caveats:
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If your random source is broken, so is the security of the messages. You have bigger problems than just this library at that point, but it's worth saying.
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The confidentiality of your messages is assured with this strategy, but there is no protection against messages being reordered and replayed by an active adversary.
Public Class Methods
Use a pair of keys to create a SimpleBox
This is a convenience method. It takes a pair of keys and instantiates a Box under the hood, then returns the new SimpleBox
.
@param public_key [PublicKey, String] The RbNaCl
public key, as class or string @param private_key [PrivateKey, String] The RbNaCl
private key, as class or string
@return [SimpleBox] Ready for use
# File lib/rbnacl/simple_box.rb, line 68 def self.from_keypair(public_key, private_key) new(Box.new(public_key, private_key)) end
Use a secret key to create a SimpleBox
This is a convenience method. It takes a secret key and instantiates a SecretBox under the hood, then returns the new SimpleBox
.
@param secret_key [String] The secret key, 32 bytes long.
@return [SimpleBox] Ready for use
# File lib/rbnacl/simple_box.rb, line 55 def self.from_secret_key(secret_key) new(SecretBox.new(secret_key)) end
Create a new SimpleBox
@param box [SecretBox, Box] the SecretBox or Box to use.
@return [SimpleBox] Ready for use
# File lib/rbnacl/simple_box.rb, line 43 def initialize(box) @box = box end
Public Instance Methods
Encrypts the message with a random nonce
Encrypts the message with a random nonce, then returns the ciphertext with the nonce prepended. Optionally encodes the message using an encoder.
@param message [String] The message to encrypt
@return [String] The enciphered message
# File lib/rbnacl/simple_box.rb, line 80 def box(message) nonce = generate_nonce cipher_text = @box.box(nonce, message) nonce + cipher_text end
Decrypts the ciphertext with a random nonce
Takes a ciphertext, optionally decodes it, then splits the nonce off the front and uses this to decrypt. Returns the message.
@param enciphered_message [String] The message to decrypt.
@raise [CryptoError] If the message has been tampered with.
@return [String] The decoded message
# File lib/rbnacl/simple_box.rb, line 97 def open(enciphered_message) nonce, ciphertext = extract_nonce(enciphered_message.to_s) @box.open(nonce, ciphertext) end
Private Instance Methods
# File lib/rbnacl/simple_box.rb, line 109 def extract_nonce(bytes) nonce = bytes.slice(0, nonce_bytes) [nonce, bytes.slice(nonce_bytes..-1)] end
# File lib/rbnacl/simple_box.rb, line 105 def generate_nonce Random.random_bytes(nonce_bytes) end