added basic libsodium public key signature sign/verify functionality

spec/cox_spec.cr

@@ -3,7 +3,7 @@ require "./spec_helper"
 describe Cox do
   # TODO: Write tests
 
-  it "works" do
+  it "works for encrypting" do
     data = "Hello World!"
 
     # Alice is the sender
@@ -22,4 +22,18 @@ describe Cox do
 
     String.new(decrypted).should eq(data)
   end
+
+  it "works for signing" do
+    message = "test"
+
+    signing_pair = Cox::SignKeyPair.new
+    
+    # Create signature using the secret key
+    signature = Cox.sign(message, signing_pair.secret)
+
+    # Verify the signature on the message
+    verified = Cox.verify(signature, message, signing_pair.public)
+
+    verified.should eq(true)
+  end
 end

src/cox.cr

@@ -22,6 +22,24 @@ module Cox
     LibSodium.crypto_box_open_easy(output_buffer.to_unsafe, data_buffer.to_unsafe, data_size, nonce.pointer, sender_public_key.pointer, recipient_secret_key.pointer)
     output_buffer
   end
+
+  def self.sign(message, secret_key : SignSecretKey)
+    message_buffer = message.to_slice
+    message_buffer_size = message_buffer.bytesize
+    signature_output_buffer = Bytes.new(LibSodium::SIGNATURE_BYTES)
+
+    LibSodium.crypto_sign_detached(signature_output_buffer.to_unsafe, 0, message_buffer.to_unsafe, message_buffer_size, secret_key.pointer)
+    signature_output_buffer
+  end
+
+  def self.verify(signature, message, public_key : SignPublicKey)
+    signature_buffer = signature.to_slice
+    message_buffer = message.to_slice
+    message_buffer_size = message_buffer.bytesize
+
+    verified = LibSodium.crypto_sign_verify_detached(signature_buffer.to_unsafe, message_buffer.to_unsafe, message_buffer_size, public_key.pointer)
+    verified.zero?
+  end
 end
 
 if Cox::LibSodium.sodium_init() == -1

src/cox/lib_sodium.cr

@@ -7,11 +7,17 @@ module Cox
     fun crypto_box_secretkeybytes() : LibC::SizeT
     fun crypto_box_noncebytes()     : LibC::SizeT
     fun crypto_box_macbytes()       : LibC::SizeT
+    fun crypto_sign_publickeybytes() : LibC::SizeT
+    fun crypto_sign_secretkeybytes() : LibC::SizeT
+    fun crypto_sign_bytes()         : LibC::SizeT
 
     PUBLIC_KEY_BYTES = crypto_box_publickeybytes()
     SECRET_KEY_BYTES = crypto_box_secretkeybytes()
     NONCE_BYTES      = crypto_box_macbytes()
     MAC_BYTES        = crypto_box_macbytes()
+    PUBLIC_SIGN_BYTES = crypto_sign_publickeybytes()
+    SECRET_SIGN_BYTES = crypto_sign_secretkeybytes()
+    SIGNATURE_BYTES  = crypto_sign_bytes()
 
     fun crypto_box_keypair(
       public_key_output : Pointer(LibC::UChar),
@@ -35,5 +41,25 @@ module Cox
       sender_public_key    : Pointer(LibC::UChar),
       recipient_secret_key : Pointer(LibC::UChar)
     ) : LibC::Int
+
+    fun crypto_sign_keypair(
+      public_key_output : Pointer(LibC::UChar),
+      secret_key_output : Pointer(LibC::UChar)
+    ) : LibC::Int
+
+    fun crypto_sign_detached(
+      signature_output      : Pointer(LibC::UChar),
+      signature_output_size : LibC::ULongLong,
+      message               : Pointer(LibC::UChar),
+      message_size          : LibC::ULongLong,
+      secret_key            : Pointer(LibC::UChar)
+    ) : LibC::Int
+
+    fun crypto_sign_verify_detached(
+      signature    : Pointer(LibC::UChar),
+      message      : Pointer(LibC::UChar),
+      message_size : LibC::ULongLong,
+      public_key   : Pointer(LibC::UChar)
+    ) : LibC::Int
   end
 end

src/cox/sign_key_pair.cr

@@ -0,0 +1,24 @@
+require "./lib_sodium"
+
+module Cox
+  class SignKeyPair
+    property public : SignPublicKey
+    property secret : SignSecretKey
+
+    def initialize(@public, @secret)
+    end
+
+    def self.new(pub : Bytes, sec : Bytes)
+      new(SignPublicKey.new(pub), SignSecretKey.new(sec))
+    end
+
+    def self.new
+      public_key = Bytes.new(SignPublicKey::KEY_LENGTH)
+      secret_key = Bytes.new(SignSecretKey::KEY_LENGTH)
+
+      LibSodium.crypto_sign_keypair(public_key.to_unsafe, secret_key.to_unsafe)
+
+      new(public_key, secret_key)
+    end
+  end
+end

src/cox/sign_public_key.cr

@@ -0,0 +1,15 @@
+require "./lib_sodium"
+
+module Cox
+  class SignPublicKey < Key
+    property bytes : Bytes
+
+    KEY_LENGTH = LibSodium::PUBLIC_SIGN_BYTES
+
+    def initialize(@bytes : Bytes)
+      if bytes.bytesize != KEY_LENGTH
+        raise ArgumentError.new("Public key must be #{KEY_LENGTH} bytes, got #{bytes.bytesize}")
+      end
+    end
+  end
+end

src/cox/sign_secret_key.cr

@@ -0,0 +1,15 @@
+require "./lib_sodium"
+
+module Cox
+  class SignSecretKey < Key
+    property bytes : Bytes
+
+    KEY_LENGTH = LibSodium::SECRET_SIGN_BYTES
+
+    def initialize(@bytes : Bytes)
+      if bytes.bytesize != KEY_LENGTH
+        raise ArgumentError.new("Secret key must be #{KEY_LENGTH} bytes, got #{bytes.bytesize}")
+      end
+    end
+  end
+end

src/cox/signature.cr

@@ -0,0 +1,15 @@
+require "./lib_sodium"
+
+module Cox
+  class Signature
+    property bytes : Bytes
+
+    KEY_LENGTH = LibSodium::SIGNATURE_BYTES
+
+    def initialize(@bytes : Bytes)
+      if bytes.bytesize != KEY_LENGTH
+        raise ArgumentError.new("Signature must be #{KEY_LENGTH} bytes, got #{bytes.bytesize}")
+      end
+    end
+  end
+end