\&\fISSL_CTX_set1_client_sigalgs_list()\fR and \fISSL_set1_client_sigalgs_list()\fR set
signature algorithms related to client authentication, otherwise they are
identical to \fISSL_CTX_set1_sigalgs()\fR, \fISSL_set1_sigalgs()\fR,
\&\fISSL_CTX_set1_sigalgs_list()\fR and \fISSL_set1_sigalgs_list()\fR.
.PP
All these functions are implemented as macros. The signature algorithm
parameter (integer array or string) is not freed: the application should
free it, if necessary.
.SH"NOTES"
.IXHeader"NOTES"
If an application wishes to allow the setting of signature algorithms
as one of many user configurable options it should consider using the more
flexible \s-1SSL_CONF\s0 \s-1API\s0 instead.
.PP
The signature algorithms set by a client are used directly in the supported
signature algorithm in the client hello message.
.PP
The supported signature algorithms set by a server are not sent to the
client but are used to determine the set of shared signature algorithms
and (if server preferences are set with \s-1SSL_OP_CIPHER_SERVER_PREFERENCE\s0)
their order.
.PP
The client authentication signature algorithms set by a server are sent
in a certificate request message if client authentication is enabled,
otherwise they are unused.
.PP
Similarly client authentication signature algorithms set by a client are
used to determined the set of client authentication shared signature
algorithms.
.PP
Signature algorithms will neither be advertised nor used if the security level
prohibits them (for example \s-1SHA1\s0 if the security level is 4 or more).
.PP
Currently the NID_md5, NID_sha1, NID_sha224, NID_sha256, NID_sha384 and
NID_sha512 digest NIDs are supported and the public key algorithm NIDs
\&\s-1EVP_PKEY_RSA\s0, \s-1EVP_PKEY_RSA_PSS\s0, \s-1EVP_PKEY_DSA\s0 and \s-1EVP_PKEY_EC\s0.
.PP
The short or long name values for digests can be used in a string (for
example \*(L"\s-1MD5\s0\*(R", \*(L"\s-1SHA1\s0\*(R", \*(L"\s-1SHA224\s0\*(R", \*(L"\s-1SHA256\s0\*(R", \*(L"\s-1SHA384\s0\*(R", \*(L"\s-1SHA512\s0\*(R") and
the public key algorithm strings \*(L"\s-1RSA\s0\*(R", \*(L"RSA-PSS\*(R", \*(L"\s-1DSA\s0\*(R" or \*(L"\s-1ECDSA\s0\*(R".
.PP
The \s-1TLS\s0 1.3 signature scheme names (such as \*(L"rsa_pss_pss_sha256\*(R") can also
be used with the \fB_list\fR forms of the \s-1API\s0.
.PP
The use of \s-1MD5\s0 as a digest is strongly discouraged due to security weaknesses.
.SH"RETURN VALUES"
.IXHeader"RETURN VALUES"
All these functions return 1 for success and 0 for failure.
.SH"EXAMPLES"
.IXHeader"EXAMPLES"
Set supported signature algorithms to \s-1SHA256\s0 with \s-1ECDSA\s0 and \s-1SHA256\s0 with \s-1RSA\s0
using an array:
.PP
.Vb1
\& const int slist[] = {NID_sha256, EVP_PKEY_EC, NID_sha256, EVP_PKEY_RSA};
\&
\& SSL_CTX_set1_sigalgs(ctx, slist, 4);
.Ve
.PP
Set supported signature algorithms to \s-1SHA256\s0 with \s-1ECDSA\s0 and \s-1SHA256\s0 with \s-1RSA\s0