[crypto] add support for ECDSA signing (#3218)

include/openthread/crypto.h

@@ -38,6 +38,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#include <openthread/error.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -103,6 +105,28 @@ void otCryptoAesCcm(const uint8_t *aKey,
                     bool           aEncrypt,
                     void *         aTag);
 
+/**
+ * This method creates ECDSA sign.
+ *
+ * @param[out]    aOutput            An output buffer where ECDSA sign should be stored.
+ * @param[inout]  aOutputLength      The length of the @p aOutput buffer.
+ * @param[in]     aInputHash         An input hash.
+ * @param[in]     aInputHashLength   The length of the @p aClaims buffer.
+ * @param[in]     aPrivateKey        A private key in PEM format.
+ * @param[in]     aPrivateKeyLength  The length of the @p aPrivateKey buffer.
+ *
+ * @retval  OT_ERROR_NONE         ECDSA sign has been created successfully.
+ * @retval  OT_ERROR_NO_BUFS      Output buffer is too small.
+ * @retval  OT_ERROR_INVALID_ARGS Private key is not valid EC Private Key.
+ * @rerval  OT_ERROR_FAILED       Error during signing.
+ */
+otError otCryptoEcdsaSign(uint8_t *      aOutput,
+                          uint16_t *     aOutputLength,
+                          const uint8_t *aInputHash,
+                          uint16_t       aInputHashLength,
+                          const uint8_t *aPrivateKey,
+                          uint16_t       aPrivateKeyLength);
+
 /**
  * @}
  *