add SHA256 support

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Francesco Albanese <Francesco.Albanese@swisscom.com>
diff --git a/include/sha256.h b/include/sha256.h
new file mode 100755
index 0000000..e38ea89
--- /dev/null
+++ b/include/sha256.h
@@ -0,0 +1,16 @@
+#ifndef _SHA256_H
+#define _SHA256_H
+
+#define SHA256_SUM_LEN	32
+
+typedef struct {
+	uint32_t total[2];
+	uint32_t state[8];
+	uint8_t buffer[64];
+} sha256_context;
+
+void sha256_starts(sha256_context * ctx);
+void sha256_update(sha256_context * ctx, uint8_t * input, uint32_t length);
+void sha256_finish(sha256_context * ctx, uint8_t digest[SHA256_SUM_LEN]);
+
+#endif /* _SHA256_H */