Fix typo in docs for mbedtls_x509write_csr_der()
diff --git a/include/mbedtls/x509_csr.h b/include/mbedtls/x509_csr.h
index 34998a3..65187f3 100644
--- a/include/mbedtls/x509_csr.h
+++ b/include/mbedtls/x509_csr.h
@@ -276,7 +276,7 @@
*
* \note f_rng may be NULL if RSA is used for signature and the
* signature is made offline (otherwise f_rng is desirable
- * for couermeasures against timing attacks).
+ * for countermeasures against timing attacks).
* ECDSA signatures always require a non-NULL f_rng.
*/
int mbedtls_x509write_csr_pem( mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,