*
* \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,