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TLS Handshake Rate Calculator

Calculate sustainable TLS handshake rate from core count, key algorithm and resumption rate, plus the round trips setup costs.

Inputs

cores
%
ms

Sustainable Handshake Rate

597,015handshakes/s

Capacity if Every Handshake Were Full

200,000handshakes/s

Signing Operations per Core

25,000ops/s

Round Trips Before Application Data

1

Handshake Latency

20.0ms

Step by step

  1. Values used

    CPU cores dedicated to TLS = 8 cores; Certificate key type = ECDSA P-256; Handshakes resumed = 70 %; TLS version = TLS 1.3 (1-RTT handshake); Network round-trip time = 20 ms

  2. TLS Handshake Rate

    handshake rate = cores × operations per core ÷ ((1 − resumption rate) + 0.05 × resumption rate), since a resumed handshake costs about 5% of a full one.

  3. Sustainable Handshake Rate

    = 597,015 handshakes/s

  4. Capacity if Every Handshake Were Full

    = 200,000 handshakes/s

  5. Signing Operations per Core

    = 25,000 ops/s

  6. Round Trips Before Application Data

    = 1

  7. Handshake Latency

    = 20.0 ms

How it works

Handshake capacity is set by asymmetric signing throughput, which depends entirely on the key algorithm and size. Resumption replaces that operation with a symmetric key derivation costing roughly a twentieth as much, so a high resumption rate multiplies effective capacity. Handshake rate — not throughput — is what falls over during a thundering-herd reconnect after a deployment, and TLS 1.3 halves the user-visible setup latency on top of that.

Formula

TLS Handshake Rate

handshake rate = cores × operations per core ÷ ((1 − resumption rate) + 0.05 × resumption rate), since a resumed handshake costs about 5% of a full one.

costFactor
Average cost of a handshake relative to a full one
roundTrips
1 for TLS 1.3, 2 for TLS 1.2, before any application byte moves

Frequently Asked Questions

How is TLS Handshake Rate calculated?

handshake rate = cores × operations per core ÷ ((1 − resumption rate) + 0.05 × resumption rate), since a resumed handshake costs about 5% of a full one. Handshake capacity is set by asymmetric signing throughput, which depends entirely on the key algorithm and size. Resumption replaces that operation with a symmetric key derivation costing roughly a twentieth as much, so a high resumption rate multiplies effective capacity.

Why does TLS Handshake Rate matter?

Handshake rate — not throughput — is what falls over during a thundering-herd reconnect after a deployment, and TLS 1.3 halves the user-visible setup latency on top of that.

What values do I need to enter?

This calculator takes 5 inputs: CPU cores dedicated to TLS, Certificate key type, Handshakes resumed, TLS version, Network round-trip time. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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