# TLS_EMPTY_RENEGOTIATION_INFO_SCSV cipher suite

> TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00,0xFF) is a signaling cipher suite value (SCSV), not a real cipher suite: clients put it in the ClientHello to signal a capability, and it never gets negotiated.

Source: https://ssl.sh/ciphers/tls-empty-renegotiation-info-scsv/
Last updated: 2026-11-10

TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00,0xFF) is a signaling cipher suite value (SCSV), not a real cipher suite: clients put it in the ClientHello to signal a capability, and it never gets negotiated.

| Field | Value |
|---|---|
| IANA | TLS_EMPTY_RENEGOTIATION_INFO_SCSV |
| Hex code | 0x00,0xFF |
| OpenSSL | Not available in OpenSSL 3.5 |
| GnuTLS | - |
| Key exchange | - |
| Authentication | - |
| Encryption | - |
| MAC | - |
| TLS versions | - |
| Rating | Signal only |
| IANA "Recommended" | N |
| References | RFC 5746 |

## What each component means

TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00,0xFF) is a signal, not a cipher suite. A client puts it in its cipher list to say it supports secure renegotiation ([RFC 5746](https://www.rfc-editor.org/rfc/rfc5746)) without sending the renegotiation_info extension, which helped with servers that choked on unknown extensions. RFC 5746 fixed the 2009 renegotiation attack (CVE-2009-3555), in which a man-in-the-middle could splice its own request in front of a victim's TLS session. TLS 1.3 removed renegotiation, so the signal only matters for TLS 1.2 and earlier.

## Why this rating

- Signaling value only; it carries no algorithms and is never negotiated.

## History and standards status

TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00,0xFF) is registered in the IANA TLS Cipher Suites registry with [RFC 5746](https://www.rfc-editor.org/rfc/rfc5746), “Transport Layer Security (TLS) Renegotiation Indication Extension” (February 2010, Standards Track) as its specification.

## How to test whether a server accepts it

Check secure renegotiation support on TLS 1.2; s_client prints “Secure Renegotiation IS supported” when the server understands it:

```bash
openssl s_client -connect example.com:443 -tls1_2 </dev/null | grep -i renegotiation
```

To decode a name or hex code, use the [cipher suite lookup](https://ssl.sh/tools/cipher-suite-lookup/); the [SSL checker](https://ssl.sh/tools/ssl-checker/) shows which protocol versions a live server accepts and the cipher suite it negotiates.

## FAQ

### Is TLS_EMPTY_RENEGOTIATION_INFO_SCSV a real cipher suite?

No. It is a signaling cipher suite value: it carries no algorithms, is never selected by the server, and only tells the server something about the client. ssl.sh therefore does not rate it.

### Do I need to configure TLS_EMPTY_RENEGOTIATION_INFO_SCSV in Nginx or Apache?

No. Clients add it automatically and OpenSSL-based servers such as Nginx and Apache httpd recognise it without any directive; it doesn't appear in `ssl_ciphers` or `SSLCipherSuite` lists.

### Does TLS_EMPTY_RENEGOTIATION_INFO_SCSV matter with TLS 1.3?

Not for TLS 1.3 connections, which have no renegotiation at all. It still matters when TLS 1.2 is negotiated, where it protects against the CVE-2009-3555 renegotiation attack.