# TLS_ASCONAEAD128_SHA256 cipher suite

> TLS_ASCONAEAD128_SHA256 (0x00,0x6F): any (negotiated separately)/any (negotiated separately) · Ascon-AEAD128 · TLS 1.3. ssl.sh rating: Secure. OpenSSL/GnuTLS names and Nginx/Apache config.

Source: https://ssl.sh/ciphers/tls-asconaead128-sha256/
Last updated: 2026-11-10

TLS_ASCONAEAD128_SHA256 (0x00,0x6F) is a TLS 1.3 cipher suite: Ascon-AEAD128 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 Secure.

| Field | Value |
|---|---|
| IANA | TLS_ASCONAEAD128_SHA256 |
| Hex code | 0x00,0x6F |
| OpenSSL | Not available in OpenSSL 3.5 |
| GnuTLS | - |
| Key exchange | any (negotiated separately) |
| Authentication | any (negotiated separately) |
| Encryption | Ascon-AEAD128 |
| MAC | AEAD |
| TLS versions | TLS 1.3 |
| Rating | Secure |
| IANA "Recommended" | N |
| References | https://doi.org/10.6028/NIST.SP.800-232, RFC 9846 |

## 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_ASCONAEAD128_SHA256 combines the Ascon-AEAD128 AEAD with 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_ASCONAEAD128_SHA256, SHA256 is the hash behind the HKDF key schedule and the handshake transcript hash.

Encryption: Ascon-AEAD128, the lightweight authenticated cipher that NIST picked in 2023 at the end of its lightweight cryptography competition and standardised in SP 800-232. It targets small devices without AES hardware.

## Why this rating

- A TLS 1.3 AEAD suite, but IANA doesn't mark it "Recommended" (truncated tag, national or experimental algorithm, or limited client support).

## Which TLS libraries support it

Support for TLS_ASCONAEAD128_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_ASCONAEAD128_SHA256 (0x00,0x6F) is registered in the IANA TLS Cipher Suites registry with [RFC 9846](https://www.rfc-editor.org/rfc/rfc9846), “The Transport Layer Security (TLS) Protocol Version 1.3” (July 2026, Standards Track) as its specification. The algorithm itself is standardised in NIST SP 800-232. TLS 1.3 was first published as [RFC 8446](https://www.rfc-editor.org/rfc/rfc8446) (2018) and republished as [RFC 9846](https://www.rfc-editor.org/rfc/rfc9846) (2026), which obsoletes RFC 8446. The registry marks it N, which per [RFC 8447](https://www.rfc-editor.org/rfc/rfc8447) (2018) means it either hasn't been through the IETF consensus process, has limited applicability or is meant only for specific use cases, not necessarily that it is flawed.

## How to test whether a server accepts it

OpenSSL 3.5 cannot offer TLS_ASCONAEAD128_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_ASCONAEAD128_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_ASCONAEAD128_SHA256 secure?

Cryptographically, yes: ssl.sh rates it secure. A TLS 1.3 AEAD suite, but IANA doesn't mark it "Recommended" (truncated tag, national or experimental algorithm, or limited client support).

### Can TLS_ASCONAEAD128_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_ASCONAEAD128_SHA256 in Nginx or Apache?

There is nothing to disable: OpenSSL 3.5, which Nginx and Apache httpd normally use, does not implement TLS_ASCONAEAD128_SHA256, so they cannot negotiate it.

### Which clients and libraries still support TLS_ASCONAEAD128_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.