Cipher Suite Strength Calculator

Work out cipher suite strength instantly with clear inputs, formula shown and shareable results.

About Cipher Suite Strength Calculator

A cipher suite is judged on three axes: the symmetric key size, whether the mode is authenticated encryption, and whether the key exchange is ephemeral. AEAD modes such as GCM and ChaCha20-Poly1305 remove the padding-oracle and MAC-then-encrypt classes of flaw that plague CBC, while ECDHE ensures a stolen server key cannot decrypt recorded traffic. 3DES additionally has a 64-bit block, limiting safe data to tens of megabytes per key.

Formula

Suite scoring

score = 45 x (symmetric bits / 256) + 30 if AEAD + 25 if forward secret; 3DES capped for its 64-bit block size

Worked example

With the default values below, Cipher Suite Strength Calculator returns Cipher suite strength score (0-100) of 100. Change any input above and every figure here is recalculated in your browser.

Inputs used

Bulk cipherone of AES-128-GCM, AES-256-GCM, ChaCha20-Poly1305, AES-128-CBC, 3DES-CBC: AES-256-GCM
Key exchangeone of ECDHE (forward secret), DHE (forward secret), Static RSA (no forward secrecy): ECDHE (forward secret)
Data per sessionminimum 0.001 GB: 10 GB

Results

Cipher suite strength score (0-100): 100
Symmetric strength: 256 bits
Forward secrecy: Yes - ephemeral key exchange
Data volume assessment: Within the safe data volume for this cipher

Step by step

1Values used
2Suite scoring
3Cipher suite strength score (0-100)= 100
4Symmetric strength= 256 bits
5Forward secrecy= Yes - ephemeral key exchange
6Data volume assessment= Within the safe data volume for this cipher

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Is AES-256 worth the cost over AES-128?

Only where policy or long-term quantum margin demands it. AES-128 has no practical attack, and on hardware without AES-NI the difference in throughput is noticeable.

When is ChaCha20-Poly1305 preferable?

On devices without AES hardware acceleration, where it is substantially faster and has more consistent timing behaviour than software AES.