diff --git a/lib/minisign.rb b/lib/minisign.rb
index eb6ab81..0a12b39 100644
--- a/lib/minisign.rb
+++ b/lib/minisign.rb
@@ -2,7 +2,6 @@
 
 require 'ed25519'
 require 'base64'
-require 'openssl'
 require 'rbnacl'
 
 require 'minisign/utils'
diff --git a/lib/minisign/utils.rb b/lib/minisign/utils.rb
index d51b63a..311b5ea 100644
--- a/lib/minisign/utils.rb
+++ b/lib/minisign/utils.rb
@@ -3,8 +3,12 @@
 module Minisign
   # Helpers used in multiple classes
   module Utils
+    def blake2b256(message)
+      RbNaCl::Hash::Blake2b.digest(message, { digest_size: 32 })
+    end
+
     def blake2b512(message)
-      OpenSSL::Digest.new('BLAKE2b512').digest(message)
+      RbNaCl::Hash::Blake2b.digest(message, { digest_size: 64 })
     end
   end
 end
diff --git a/spec/minisign/private_key_spec.rb b/spec/minisign/private_key_spec.rb
index 95bb724..de55977 100644
--- a/spec/minisign/private_key_spec.rb
+++ b/spec/minisign/private_key_spec.rb
@@ -68,8 +68,7 @@
         @private_key.public_key
       ].inject(&:+).pack('C*')
 
-      computed_checksum = RbNaCl::Hash::Blake2b.digest(key_data, { digest_size: 32 }).bytes
-
+      computed_checksum = blake2b256(key_data).bytes
       expect(@private_key.checksum).to eq(computed_checksum)
     end
   end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 8a06978..19c3de1 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -8,6 +8,7 @@
 require 'minisign'
 
 RSpec.configure do |config|
+  config.include Minisign::Utils
   config.expect_with :rspec do |expectations|
     expectations.include_chain_clauses_in_custom_matcher_descriptions = true
   end