TLS Cipher Suite Analyzer

See the TLS version and cipher suite a server negotiates, graded for forward secrecy, authenticated encryption and deprecated primitives.

Passive public check

a2z.tools reads publicly visible information from the address you enter. It is a read-only request - nothing is submitted, changed or probed.

Domain Opens real TLS handshakes to see which protocol versions and cipher suite the server negotiates.

What the server actually negotiates

This opens real TLS handshakes - one to see what the server picks when offered everything, and several more to find out which protocol versions it will accept at all. It reuses the same inspector that powers SSL/TLS Checker and TLS Version Checker, so the three agree by construction.

Nothing is sent beyond the handshake itself, and the connection is closed immediately after.

Forward secrecy is the property that matters most

A cipher suite using an ephemeral key exchange - ECDHE or DHE - generates fresh keys for every session and throws them away afterwards. Without one, the session key is derived using the server's long-term private key, which means anyone who records traffic today and later obtains that key can decrypt all of it retrospectively.

That is the difference between a key compromise being a future problem and a retrospective one, and it is why this is graded high rather than medium when it is missing.

Authenticated encryption

AEAD suites - AES-GCM, ChaCha20-Poly1305, AES-CCM - encrypt and authenticate in one operation. The older CBC-mode construction in TLS 1.2 and earlier separates the two, and that separation has produced a long line of padding-oracle attacks: BEAST, Lucky13 and successors. The attacks are mitigated in practice rather than eliminated, so an AEAD suite is simply the better choice.

TLS 1.3 removes the question

Every TLS 1.3 cipher suite provides forward secrecy and uses authenticated encryption. The protocol removed the alternatives rather than deprecating them, so there is no weak choice to make. If a server negotiates TLS 1.3, this tool reports the suite as a pass without further analysis, because there is nothing to analyse.

Deprecated protocol versions

RFC 8996 formally deprecated TLS 1.0 and 1.1 in 2021. Accepting them keeps a downgrade path open and fails most compliance regimes including PCI DSS. Current browsers already refuse them, so leaving them enabled rarely serves anyone - it mostly serves scanners.

Key and signature strength

The tool also reports the certificate's key algorithm and size, and its signature algorithm. RSA below 2048 bits and ECDSA below P-256 are both below current minimums. A certificate signed with SHA-1 or MD5 is reported as critical - both are practically collidable, and every browser has rejected SHA-1 certificates since 2017, so such a certificate is almost certainly already failing for real visitors.

Generate the configuration

Once you know what to change, TLS Configuration Generator produces the configuration for Nginx, Apache, IIS, ASP.NET Core or Node, with the client compatibility each profile costs you stated explicitly.

Frequently asked questions

Does this send any data to my server?

Only TLS handshakes. No HTTP request is made, nothing is submitted, and the connection closes as soon as the handshake completes.

Why does it open several connections?

One to see what the server negotiates when offered everything, and one per protocol version to find out which it will accept. There is no way to determine accepted versions without attempting them.

My server negotiated TLS 1.3 and the suite was not analysed. Why?

Because there is nothing to analyse. All five TLS 1.3 suites provide forward secrecy and authenticated encryption - the protocol removed the weak options entirely.

Is CBC actually broken?

Not outright, but the attacks against it are a recurring family rather than a single fixed bug, and mitigations are implementation-dependent. AEAD suites do not have that class of problem, so there is no reason to prefer CBC.

References

Related tools

What this tool can and cannot tell you. It reports the configuration a site exposes to an ordinary visitor. It does not log in, submit anything, or test for vulnerabilities, so a passing result means the public configuration looked correct at the moment of the check - not that the site is secure.

Security guidance here follows current published sources - OWASP, MDN, the relevant RFCs, NIST, CISA, FIRST and MITRE - which are linked beside the specific claims they support.