Source: https://guthlabs.ai/docs/instruments/password-passphrase-entropy-estimator/implementation/

instrument implementation / implementation-contract

# Password / Passphrase Entropy Estimator implementation

A source-bound implementation contract for Password / Passphrase Entropy Estimator; deployment and executable qualification remain separate.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-with-binding-errata

**Evidence ID**: t4-088

**Effect**: Computation or source lookup only

## Input and validation requirements

Invalid zero guess rates can trigger undefined division, and the specification leaves exhaustive-versus-average crack time and rate-unit conventions insufficiently explicit. Zero-length input also requires explicit weak/invalid handling.

## Required corrections

````
[
  {
    "vector": 2,
    "field": "exhaustive_crack_time_seconds",
    "wrong": 475920.314814,
    "correct": 475920314800000,
    "cause": "94^12/1e9 dropped a factor of 1e9 (v1/v3 crack times correct)"
  }
]
````

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "mode": "charset",
    "charset_size": 26,
    "length": 8,
    "guesses_per_sec": 1000000000
  },
  "expected_outputs": {
    "entropy_bits": 37.6035177451,
    "exhaustive_crack_time_seconds": 208.827064576
  },
  "working": "H = L·log2(N) = 8·log2(26) = 8·4.70043971814 = 37.6035177451 bits. Search space = 2^H = 26^8 = 208,827,064,576 guesses. Time = 208,827,064,576 / 1,000,000,000 = 208.827064576 seconds."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/password-passphrase-entropy-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/password-passphrase-entropy-estimator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/password-passphrase-entropy-estimator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`

- `tranche errata record`