sshsig_signer
const char *sig_namespace, const char *hashalg, sshsig_signer *signer,
sshsig_signer *signer = NULL;
sshsig_signer *signer, void *signer_ctx)
struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
sshsig_signer *signer, void *signer_ctx)
sshsig_signer *signer, void *signer_ctx);
struct sshbuf **out, sshsig_signer *signer, void *signer_ctx);