3 files changed, 64 insertions, 28 deletions

diff --git a/include/sha.h b/include/sha.h
new file mode 100644
index 0000000..255c769
--- /dev/null
+++ b/include/sha.h
@@ -0,0 +1,57 @@
+// This file is part of a crypto library, exam for the Algorithms class.
+// All of these files are under MIT license.
+//
+// SHA declaration document:
+// https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf
+
+#ifndef HMACSHA256_SHA_H_
+#define HMACSHA256_SHA_H_
+
+#include<cstdint>
+#include<array>
+
+namespace hmacsha256 {
+class SHA {
+public:
+    SHA() {
+        digest_ = new uint8_t[32];
+    }
+
+    ~SHA() {
+        delete digest_;
+    }
+
+    // get digest as array of bytes
+    virtual uint8_t* digest() = 0;
+
+    virtual std::string hexdigest() = 0;
+protected:
+    uint8_t* digest_;
+
+    // work variables: a, b, c, d, e, f, g, h
+    uint32_t vars_[8];
+
+    // data message, in bytes
+    // M,  "message to be hashed"
+    uint8_t message_[64];
+
+    // length L of the original message
+    uint32_t message_l_;
+
+    // lenght of bits
+    uint64_t bit_len_;
+
+    // the constructor
+    virtual void init(const uint8_t* data, uint32_t length) = 0;
+
+    // padding
+    virtual void pad() = 0;
+
+    // main function
+    virtual void transform() = 0;
+};
+
+
+} // namespace hmacsha256
+
+#endif // HMACSHA256_SHA_H_
diff --git a/include/sha256.h b/include/sha256.h
index c02eb40..921a50f 100644
--- a/include/sha256.h
+++ b/include/sha256.h
@@ -9,37 +9,21 @@
 
 #include<cstdint>
 #include<array>
+#include "sha.h"
 
 namespace hmacsha256 {
-class SHA256 {
+class SHA256 : public SHA {
 public:
     // create a new SHA256 thanks an array of bytes
     SHA256(const uint8_t*, uint32_t);
 
     SHA256(const std::string&);
 
-    ~SHA256();
-
     // get digest as array of bytes
-    uint8_t* digest();
+    uint8_t* digest() override;
 
-    std::string hexdigest();
+    std::string hexdigest() override;
 private:
-    uint8_t* digest_;
-
-    // work variables: a, b, c, d, e, f, g, h
-    uint32_t vars_[8];
-
-    // data message, in bytes
-    // M,  "message to be hashed"
-    uint8_t message_[64];
-
-    // length L of the original message
-    uint32_t message_l_;
-
-    // lengh of bits
-    uint64_t bit_len_;
-
     // first 80 costansts 64bit words, paragraph 4.2.2
     std::array<uint32_t, 64> K = {
         0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,
@@ -61,7 +45,7 @@ private:
     };
 
     // the constructor
-    void init(const uint8_t* data, uint32_t length);
+    void init(const uint8_t* data, uint32_t length) override;
 
     // Ch(x, y, z) = (x | y) ^ (~x & z)
     static uint32_t ch(uint32_t, uint32_t, uint32_t);
@@ -90,10 +74,10 @@ private:
     static uint32_t sigma1(uint32_t);
 
     // padding
-    void pad();
+    void pad() override;
 
     // main function
-    void transform();
+    void transform() override;
 
     // transform bytes in big-endian, because SHA256 wants big endian ordering
     // Takes 1 parameter, the array of bytes that we want to reorder
diff --git a/src/sha256.cc b/src/sha256.cc
index 7ef467e..7790f8a 100644
--- a/src/sha256.cc
+++ b/src/sha256.cc
@@ -8,7 +8,6 @@ hmacsha256::SHA256::SHA256(const uint8_t* data, uint32_t length) {
 }
 
 void hmacsha256::SHA256::init(const uint8_t* data, uint32_t length) {
-    digest_ = new uint8_t[32];
     message_l_ = bit_len_ = 0;
     vars_[0] = 0x6a09e667;
     vars_[1] = 0xbb67ae85;
@@ -30,10 +29,6 @@ void hmacsha256::SHA256::init(const uint8_t* data, uint32_t length) {
     }
 }
 
-hmacsha256::SHA256::~SHA256() {
-    delete digest_;
-}
-
 hmacsha256::SHA256::SHA256(const std::string& data) {
     init(reinterpret_cast<const uint8_t*> (data.c_str()), data.size());
 }