cmp_ctx_set_md
if (!cmp_ctx_set_md(ctx, &ctx->pbm_owf, NID_sha256))
if (!cmp_ctx_set_md(ctx, &ctx->digest, NID_sha256))
if (!cmp_ctx_set_md(ctx, &ctx->digest, val))
if (!cmp_ctx_set_md(ctx, &ctx->pbm_owf, val))