diff --git a/tests/unit-tests/security/digest-sha256.t.cpp b/tests/unit-tests/security/digest-sha256.t.cpp
index ebf50c7..ffc6908 100644
--- a/tests/unit-tests/security/digest-sha256.t.cpp
+++ b/tests/unit-tests/security/digest-sha256.t.cpp
@@ -22,7 +22,8 @@
 #include "security/digest-sha256.hpp"
 #include "security/key-chain.hpp"
 #include "security/validator.hpp"
-#include "security/cryptopp.hpp"
+#include "util/string-helper.hpp"
+
 #include "identity-management-fixture.hpp"
 #include "boost-test.hpp"
 
@@ -39,10 +40,8 @@
 
   char content[6] = "1234\n";
   ConstBufferPtr buf = crypto::sha256(reinterpret_cast<uint8_t*>(content), 5);
-  std::string result;
-  StringSource(buf->buf(), buf->size(), true, new HexEncoder(new StringSink(result), false));
 
-  BOOST_CHECK_EQUAL(SHA256_RESULT, result);
+  BOOST_CHECK_EQUAL(SHA256_RESULT, toHex(buf->buf(), buf->size(), false));
 }
 
 BOOST_AUTO_TEST_CASE(DataSignature)
diff --git a/tests/unit-tests/security/pib-data-fixture.cpp b/tests/unit-tests/security/pib-data-fixture.cpp
index a42c0e3..dfb5304 100644
--- a/tests/unit-tests/security/pib-data-fixture.cpp
+++ b/tests/unit-tests/security/pib-data-fixture.cpp
@@ -79,10 +79,7 @@
  *   {
  *     using namespace CryptoPP;
  *
- *     std::stringstream ss;
- *     StringSource(buf, size, true, new HexEncoder(new FileSink(ss)));
- *
- *     std::string hex = ss.str();
+ *     std::string hex = toHex(buf, size);
  *
  *     for (int i = 0; i < hex.size(); i++) {
  *       if (i % 40 == 0)