diff --git a/libraries/MySensors/MySensor.h b/libraries/MySensors/MySensor.h
index cff8ead..2833f5a 100644
--- a/libraries/MySensors/MySensor.h
+++ b/libraries/MySensors/MySensor.h
@@ -98,6 +98,7 @@
 	#define MY_SIGNING_FEATURE
 #endif
 #include "core/MySigning.cpp"
+#include "drivers/ATSHA204/sha256.cpp"
 #if defined(MY_SIGNING_FEATURE)
 	// SIGNING COMMON FUNCTIONS
 	#if defined(MY_SIGNING_ATSHA204) && defined(MY_SIGNING_SOFT)
@@ -109,7 +110,6 @@
 		#include "drivers/ATSHA204/ATSHA204.cpp"
 	#elif defined(MY_SIGNING_SOFT)
 		#include "core/MySigningAtsha204Soft.cpp"
-		#include "drivers/ATSHA204/sha256.cpp"
 	#endif
 #endif
 
diff --git a/libraries/MySensors/core/MySigning.cpp b/libraries/MySensors/core/MySigning.cpp
index c54f199..6e95b4a 100644
--- a/libraries/MySensors/core/MySigning.cpp
+++ b/libraries/MySensors/core/MySigning.cpp
@@ -18,6 +18,7 @@
  */
 
 #include "MySigning.h"
+#include "drivers/ATSHA204/sha256.h"
 
 #if defined(MY_DEBUG_VERBOSE)
 #define SIGN_DEBUG(x,...) debug(x, ##__VA_ARGS__)
@@ -308,3 +309,22 @@ bool signerVerifyMsg(MyMessage &msg) {
 #endif // MY_SIGNING_REQUEST_SIGNATURES
 	return verificationResult;
 }
+
+static uint8_t sha256_hash[32];
+Sha256Class _soft_sha256;
+
+void signerSha256Init(void) {
+	memset(sha256_hash, 0, 32);
+	_soft_sha256.init();
+}
+
+void signerSha256Update(const uint8_t* data, size_t sz) {
+	for (size_t i = 0; i < sz; i++) {
+		_soft_sha256.write(data[i]);
+	}
+}
+
+uint8_t* signerSha256Final(void) {
+	memcpy(sha256_hash, _soft_sha256.result(), 32);
+	return sha256_hash;
+}
diff --git a/libraries/MySensors/core/MySigning.h b/libraries/MySensors/core/MySigning.h
index d2595e5..4f69c81 100644
--- a/libraries/MySensors/core/MySigning.h
+++ b/libraries/MySensors/core/MySigning.h
@@ -581,5 +581,32 @@ bool signerSignMsg(MyMessage &msg);
  */
 bool signerVerifyMsg(MyMessage &msg);
 
+/**
+ * @brief Initialize a hash calculation session.
+ *
+ * Any ongoing calculation session will be terminated/reset.
+ */
+void signerSha256Init(void);
+
+/**
+ * @brief Add data to an ongoing hash calculation session.
+ *
+ * More data can be added by repeated calls to this function.
+ *
+ * @param data Buffer with data to add.
+ * @param sz Size of data buffer.
+ */
+void signerSha256Update(const uint8_t* data, size_t sz);
+
+/**
+ * @brief Finalize an ongong hash calculation session and return the hash.
+ *
+ * The returned hash size is always 32 bytes. Buffer can be assumed to be valid
+ * until @ref signerSha256Init() is called again.
+ *
+ * @returns Buffer with 32-byte hash.
+ */
+uint8_t* signerSha256Final(void);
+
 #endif
 /** @}*/
\ No newline at end of file
diff --git a/libraries/MySensors/drivers/ATSHA204/sha256.h b/libraries/MySensors/drivers/ATSHA204/sha256.h
index c0e3ef9..730e11d 100644
--- a/libraries/MySensors/drivers/ATSHA204/sha256.h
+++ b/libraries/MySensors/drivers/ATSHA204/sha256.h
@@ -23,7 +23,7 @@ class Sha256Class
     void initHmac(const uint8_t* secret, int secretLength);
     uint8_t* result(void);
     uint8_t* resultHmac(void);
-    virtual void write(uint8_t);
+    void write(uint8_t);
   private:
     void pad();
     void addUncounted(uint8_t data);