this case \fICURLOPT_SSLKEY(3)\fP is used as an identifier passed to the
engine. You have to set the crypto engine with \fICURLOPT_SSLENGINE(3)\fP.
\&"DER" format key file currently does not work because of a bug in OpenSSL.
+
+The application does not have to keep the string around after setting this
+option.
.SH DEFAULT
"PEM"
.SH PROTOCOLS