# TLS_SHA256_SHA256 cipher suite

> TLS_SHA256_SHA256 (0xC0,0xB4): any (negotiated separately)/any (negotiated separately) · NULL · TLS 1.3. ssl.sh rating: Insecure. OpenSSL/GnuTLS names and Nginx/Apache config.

Source: https://ssl.sh/ciphers/tls-sha256-sha256/
Last updated: 2026-11-10

TLS_SHA256_SHA256 (0xC0,0xB4) is a TLS 1.3 cipher suite: NULL authenticated encryption with SHA256 as the HKDF hash. In TLS 1.3 the key exchange and authentication are negotiated separately, so the suite name doesn't contain them. ssl.sh rates it Insecure.

| Field | Value |
|---|---|
| IANA | TLS_SHA256_SHA256 |
| Hex code | 0xC0,0xB4 |
| OpenSSL | Not available in OpenSSL 3.5 |
| GnuTLS | - |
| Key exchange | any (negotiated separately) |
| Authentication | any (negotiated separately) |
| Encryption | NULL |
| MAC | HMAC-SHA256 |
| TLS versions | TLS 1.3 |
| Rating | Insecure |
| IANA "Recommended" | D |
| References | RFC 9150, RFC 9847 |

## What each component means

A [cipher suite](https://ssl.sh/glossary/cipher-suite/) names the algorithms a client and server agree on in one handshake. TLS_SHA256_SHA256 combines HMAC-SHA256 integrity protection without any encryption, plus the SHA256 hash. Each part is explained below with its known weaknesses; for the bigger picture see [how cipher suites work](https://ssl.sh/learn/cipher-suites/).

TLS 1.3 suites only describe the symmetric part. The TLS 1.3 specification ([RFC 9846](https://www.rfc-editor.org/rfc/rfc9846)) says its suites specify only the symmetric ciphers and cannot be used with TLS 1.2. Key exchange is negotiated separately through the supported_groups and key_share extensions (for example X25519, P-256 or the hybrid X25519MLKEM768) and is always ephemeral (EC)DHE unless a client resumes in the PSK-only psk_ke mode, so a full handshake always has [forward secrecy](https://ssl.sh/glossary/forward-secrecy/). The certificate signature algorithm (for example RSA-PSS, [ECDSA](https://ssl.sh/glossary/ecdsa/) or Ed25519) is negotiated with signature_algorithms. In TLS_SHA256_SHA256, SHA256 is the hash behind the HKDF key schedule and the handshake transcript hash.

Encryption: none. TLS_SHA256_SHA256 is one of the two integrity-only TLS 1.3 suites of [RFC 9150](https://www.rfc-editor.org/rfc/rfc9150) (2022): records are authenticated with HMAC-SHA256 but sent in clear, for IoT and industrial settings that need integrity without confidentiality. The RFC itself states that the approach is not endorsed by the IETF and has no IETF consensus.

## Why this rating

- No encryption (NULL cipher): traffic is sent in clear text.

## Which TLS libraries support it

Support for TLS_SHA256_SHA256 as read from each library's own source code or official documentation on 2026-11-10. “Enabled by default” means the library negotiates it with no configuration; “off by default” means it is implemented but has to be switched on.

| Library | Status | Details |
|---|---|---|
| OpenSSL 3.5 | Not supported | - |
| GnuTLS | Not supported | - |
| BoringSSL | Not supported | - |
| Go crypto/tls | Not supported | - |
| NSS 3.133 | Not supported | - |
| Firefox | Not supported | - |
| Java 21 (SunJSSE) | Not supported | - |
| Windows Schannel (Windows 11 / Server 2022) | Not supported | - |
| rustls 0.23.46 | Not supported | - |

None of the 9 libraries tracked here enables it by default. None of them implements it.

NSS shows the library's own defaults; Firefox switches every NSS suite off at start-up and re-enables only those with a security.ssl3.* or security.tls13.* preference. Java defaults are derived from the jdk.tls.disabledAlgorithms value Oracle documents for JDK 21, which later updates may extend. The OpenSSL and GnuTLS rows only show whether the suite is implemented.

- [BoringSSL — ssl/ssl_cipher.cc (main)](https://boringssl.googlesource.com/boringssl/+/refs/heads/main/ssl/ssl_cipher.cc) (2026-11-10)
- [Go — src/crypto/tls/cipher_suites.go (master)](https://github.com/golang/go/blob/master/src/crypto/tls/cipher_suites.go) (2026-11-10)
- [Go — src/crypto/tls/defaults.go (master)](https://github.com/golang/go/blob/master/src/crypto/tls/defaults.go) (2026-11-10)
- [NSS — lib/ssl/ssl3con.c (as vendored in Firefox)](https://github.com/mozilla-firefox/firefox/blob/main/security/nss/lib/ssl/ssl3con.c) (2026-11-10)
- [NSS — TAG-INFO](https://github.com/mozilla-firefox/firefox/blob/main/security/nss/TAG-INFO) (2026-11-10)
- [Firefox — security/manager/ssl/nsNSSComponent.cpp](https://github.com/mozilla-firefox/firefox/blob/main/security/manager/ssl/nsNSSComponent.cpp) (2026-11-10)
- [Firefox — modules/libpref/init/StaticPrefList.yaml](https://github.com/mozilla-firefox/firefox/blob/main/modules/libpref/init/StaticPrefList.yaml) (2026-11-10)
- [Oracle — JDK 21 Providers Documentation: SunJSSE Cipher Suites](https://docs.oracle.com/en/java/javase/21/security/oracle-providers.html#GUID-7093246A-31A3-4304-AC5F-5FB6400405E2) (2026-11-10)
- [Oracle — JDK 21 JSSE Reference Guide: jdk.tls.disabledAlgorithms](https://docs.oracle.com/en/java/javase/21/security/java-secure-socket-extension-jsse-reference-guide.html) (2026-11-10)
- [Microsoft Learn — TLS Cipher Suites in Windows 11](https://learn.microsoft.com/en-us/windows/win32/secauthn/tls-cipher-suites-in-windows-11) (2026-11-10)
- [Microsoft Learn — TLS Cipher Suites in Windows Server 2022](https://learn.microsoft.com/en-us/windows/win32/secauthn/tls-cipher-suites-in-windows-server-2022) (2026-11-10)
- [docs.rs — rustls 0.23.46 crypto::aws_lc_rs (default provider)](https://docs.rs/rustls/0.23.46/src/rustls/crypto/aws_lc_rs/mod.rs.html) (2026-11-10)

## History and standards status

TLS_SHA256_SHA256 (0xC0,0xB4) is registered in the IANA TLS Cipher Suites registry with [RFC 9150](https://www.rfc-editor.org/rfc/rfc9150), “TLS 1.3 Authentication and Integrity-Only Cipher Suites” (April 2022, Informational) as its specification. The registry marks it D (discouraged), a value introduced by [RFC 9847](https://www.rfc-editor.org/rfc/rfc9847) (2025).

## How to test whether a server accepts it

OpenSSL 3.5 cannot offer TLS_SHA256_SHA256, so openssl s_client can't test it directly; use a scanner that implements the suite itself.

nmap's ssl-enum-ciphers script connects repeatedly, trying one suite at a time, and lists every suite the server accepts with a grade from A to F. Look for TLS_SHA256_SHA256 in its output:

```bash
nmap --script ssl-enum-ciphers -p 443 example.com
```

If your nmap build doesn't print a TLS 1.3 section, rely on the openssl command instead.

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_SHA256_SHA256 secure?

No. ssl.sh rates it insecure. No encryption (NULL cipher): traffic is sent in clear text.

### Can TLS_SHA256_SHA256 be used with TLS 1.3?

Yes. It is a TLS 1.3 suite, so it only works with TLS 1.3; a TLS 1.2 handshake cannot negotiate it. OpenSSL 3.5 doesn't implement it, so stock Nginx and Apache httpd cannot offer it.

### How do I disable TLS_SHA256_SHA256 in Nginx or Apache?

There is nothing to disable: OpenSSL 3.5, which Nginx and Apache httpd normally use, does not implement TLS_SHA256_SHA256, so they cannot negotiate it.

### Which clients and libraries still support TLS_SHA256_SHA256?

Not supported: OpenSSL 3.5, GnuTLS, BoringSSL, Go crypto/tls, NSS 3.133, Firefox, Java 21 (SunJSSE), Windows Schannel (Windows 11 / Server 2022) and rustls 0.23.46.