# John D. Cook Consulting

> Consulting service offerings: HIPAA expert determination, applied mathematics (mathematical modeling, signal processing, numerical analysis), statistical analysis, and expert testimony in these areas.

This file lists the main consulting services and technical topics covered on johndcook.com. The site focuses on applied mathematics, statistics, cryptography, and data privacy, with an emphasis on consulting services, expert testimony, and technical explanation of complex mathematical and statistical topics.

## Main site

- [Homepage](https://www.johndcook.com/)
- [Blog index](https://www.johndcook.com/blog/)

## Topics

Major consulting areas and technical domains covered on this site.

- HIPAA expert determination
- Data privacy and deidentification
- Differential privacy
- Applied mathematics consulting
- Statistical analysis
- Cryptography
- Cryptocurrency
- Standards compliance (ASTM, CLSI)
- Expert statistical testimony

## Core consulting services

- [HIPAA expert determination](https://www.johndcook.com/blog/expert-hipaa-deidentification/)
- [Data privacy consulting](https://www.johndcook.com/blog/data-privacy/)
- [Applied mathematics consulting](https://www.johndcook.com/blog/applied-math/)
- [Statistical consulting](https://www.johndcook.com/blog/applied-statistics/)
- [Expert testimony](https://www.johndcook.com/blog/expert-testimony/)

## Data privacy
- [Data privacy consulting](https://www.johndcook.com/blog/data-privacy/): Data privacy overview
- [HIPAA deidentification expert](https://www.johndcook.com/blog/expert-hipaa-deidentification/): Consulting services to offer HIPAA expert determination per 45 CFR § 164.514(b)(1).
- [HIPAA Safe Harbor](https://www.johndcook.com/blog/hipaa-identifiers-explained/): The Safe Harbor provision of the HIPAA Privacy Rule, 45 CFR § 164.514(b)(2). The 18 categories of data disallowed and the subtle 19th rule, the so-called "actual knowledge" rule.
- [Differential privacy overview](https://www.johndcook.com/blog/differential-privacy/): A high-level explanation of differential privacy
- [Mathematics of differential privacy](https://www.johndcook.com/blog/2018/11/06/what-is-differential-privacy/): An overview of the mathematics of differential privacy, enough detail to appreciate what's going on but still easy to read and not too much detail.
- [Data Privacy FAQ](https://www.johndcook.com/blog/data-privacy-faq/): Frequently asked questions about data privacy
- [Data Breach Response](https://www.johndcook.com/blog/data-incident-breach-response/): Expert consulting for evaluating whether individuals could be identified from leaked data
- [TDPSA](https://www.johndcook.com/blog/tdpsa/): Expert consulting for complying with the Texas Data Privacy and Security Act (TDPSA) 
- [Illinois Biometric Information Privacy Act](https://www.johndcook.com/blog/illinois-bipa/): Expert consulting for complying with the Illinois Biometric Information Privacy Act (740 ILCS 14, a.k.a BIPA)
- [Deidentification, anonymization, and pseudonymization](https://www.johndcook.com/blog/pseudonymization/): The terms deidentification, anonymization, and pseudonymization are confusingly similar. What do they mean and how do they differ?
- [PSQIA expert determination](https://www.johndcook.com/blog/psqia/): Expert determination for the Patient Safety and Quality Improvement Act (PSQIA)

## Cryptography
- [Random number generator testing](https://www.johndcook.com/blog/rng-testing/): Testing services for random number generators and random bit generators. Running standard test suites such as DIEHARD, DIEHARDER, NIST Statistical Test Suite (STS), Practically Random (PractRand), and TestU01 (BigCrush).
- [From now until quantum](https://www.johndcook.com/blog/2019/05/23/nsa-recommendations/): NSA cryptography recommendations for the transition from now until the adoption of quantum-resistant cryptography
- [Feistel networks](https://www.johndcook.com/blog/2020/04/04/feistel-networks/): Brief explanation of Feistel networks used in symmetric encryption.
- [ASCII armor](https://www.johndcook.com/blog/2023/12/11/ascii-armor/): How to use the ASCII armor tool to send encrypted information over an insecure channel, such as email, by converting the binary encryption output to ASCII text
- [Illustrating cryptographic strength](https://www.johndcook.com/blog/2025/09/02/cryptographic-strength/): A way of describing and comparing the strength of various encryption methods. How much water one could boil with the energy necessary to break the encryption.
- [Homomorphic encryption](https://www.johndcook.com/blog/2019/07/04/homomorphic-encryption/): A brief overview of homomorphic encryption

## Cryptocurrency
- [Monero stealth addresses](https://www.johndcook.com/blog/2025/11/24/monero-stealth-addresses/): Brief explanation of stealth addresses in the Monero cryptocurrency
- [Monero subaddresses](https://www.johndcook.com/blog/2025/11/28/monero-subaddresses/): A brief explanation of Monero subaddresses
- [What's in your wallet?](https://www.johndcook.com/blog/2025/08/16/whats-in-your-wallet/): Explaining what a cryptocurrency wallet actually stores
- [Elliptic curves in ZKP](https://www.johndcook.com/blog/2025/08/01/jubjub/): An overview of some of the elliptic curves used in zero knowledge proofs
- [Pedersen commitments](https://www.johndcook.com/blog/2025/12/06/pedersen-commitment/): A simple explanation of what a Pedersen commitment is
- [Bitcoin proof of work](https://www.johndcook.com/blog/2025/06/20/bitcoin-proof-of-work/): A detailed explanation of what exactly is the Bitcoin proof of work problem
- [Why hash puzzles](https://www.johndcook.com/blog/2025/06/22/why-hash-puzzles/): Why blockchains use hash puzzles for proof of work
- [Elliptic curve pairings](https://www.johndcook.com/blog/2025/11/16/elliptic-curve-pairings/): An introduction to elliptic curve pairings and how they are used in cryptocurrencies
- [How blockchains are chained](https://www.johndcook.com/blog/2025/10/27/blockchain/): A detailed explanation of how exactly blocks are chained together in a blockchain

## Applied mathematics
- [Numerical analysis](https://www.johndcook.com/blog/numerical-computation/): Overview of numerical analysis consulting services. Bringing together rigorous numerical computing and quality software development
- [Differential equations](https://www.johndcook.com/blog/partial-differential-equations/): Overview of consulting services around differential equations
- [Signal processing](https://www.johndcook.com/blog/digital-signal-processing-and-time-series-analysis/): Overview of consulting services around signal processing and time series analysis
- [Applied category theory](https://www.johndcook.com/blog/applied-category-theory/): Consulting services using category theory for modeling and for error detection
- [Applied complex analysis](https://www.johndcook.com/blog/applied-complex-analysis/): Consulting in applications of complex variable techniques to problem solving
- [Applied functional analysis](https://www.johndcook.com/blog/applied-functional-analysis/): Consulting using techniques from functional analysis to solve practical problems
- [Applied linear algebra](https://www.johndcook.com/blog/applied-linear-algebra/): Consulting services for applying linear algebra to solving practical problems. Numerical analysis for large-scale linear algebra
- [Applied number theory](https://www.johndcook.com/blog/applied-number-theory/): Consulting for application of number theory to practical areas such as error correcting codes, numerical integration, computer arithmetic, and random and quasi-random number generation
- [Kalman filters and tracking](https://www.johndcook.com/blog/applied-kalman-filtering/): Expert consulting for constructing and evaluating Kalman filters and generalizations such as EKF, UKF, and particle filters.
- [Numerical integration](https://www.johndcook.com/blog/numerical-integration/): Expert help with numerical integration problems.
- [Probability modeling](https://www.johndcook.com/blog/probability-modeling/): Expert consulting for constructing and evaluating probability models
- [Defensible randomization](https://www.johndcook.com/blog/defensible-randomization/): Expert guidance for creating randomization procedures that will stand up in court if challenged
- [Randomization consulting](https://www.johndcook.com/blog/randomization/): Expert guidance for creating randomization schemes and Monte Carlo simulation

## Statistical analysis
- [Biostatistics](https://www.johndcook.com/blog/expert-consultant-in-biomathematics-and-biostatistics/): Overview of biostatistics consulting services
- [Statistical OSINT](https://www.johndcook.com/blog/statistical-osint/): Consulting services involving the application of statistical analysis to open source intelligence (OSINT)
- [Real world data](https://www.johndcook.com/blog/real-world-data/): Consulting services for analysis of real world data
- [Experimental design](https://www.johndcook.com/blog/design/): Consulting services for designing experiments
- [Bayesian analysis](https://www.johndcook.com/blog/bayesian-consulting/): Consulting services for Bayesian statistics
- [Applied linear regression](https://www.johndcook.com/blog/applied-linear-regression/): Why linear regression is not as simple as it sounds. Consulting services for applying linear regression
- [Bayesian networks and causal analysis](https://www.johndcook.com/blog/bayesian-networks-causal-inference/): Consulting using Bayesian networks and causal inference to visualize and reason about complex relationships
- [Big logic](https://www.johndcook.com/blog/applied-logic/): Consulting using logic programming and Boolean satisfiability (SAT) solvers to reason about large complex systems
- [Engineering statistics](https://www.johndcook.com/blog/applied-engineering-statistics/): Consulting services for applications of statistics to engineering problems. Help for engineers who know just enough about statistics to be dangerous.
- [Response surface models](https://www.johndcook.com/blog/response-surface/): Expert consulting for Response Surface Methodology (RSM) 

## Standards compliance
- [ASTM compliance](https://www.johndcook.com/blog/astm-statistics/): Statistical consulting for complying with ASTM standards
  - ASTM D6299 - statistical QC/control charting for analytical measurement systems notes that for non-Gaussian processes, users should consult a statistician about appropriate transformations/approaches.
  - ASTM D6617 - laboratory bias detection using a single test result from a standard material
  - ASTM D7366-08 - estimating measurement uncertainty for regression-based methods 
  - ASTM E178-21 - dealing with outlying observations
  - ASTM E691 - Interlaboratory studies to determine precision 
  - ASTM D1749 - Interlaboratory evaluation of test methods used with paper/paper products
  - ASTM D2904 - Interlaboratory testing of a textile test method with normally distributed data
  - ASTM D6300 - Determination of precision and bias data for petroleum products/liquid fuels/lubricants
  - ASTM E2696 - Life and reliability testing based on the exponential distribution 
  - ASTM C1215 - Preparing/interpreting precision & bias statements 
- [CLSI compliance](https://www.johndcook.com/blog/clsi-statistics/): Statistical consulting for complying with Clinical and Laboratory Standards Institute (CLSI) standards
  - CLSI EP05-A3 - precision of quantitative measurement procedures
  - CLSI EP12-A - qualitative test performance protocol
  - CLSI EP17-A2 - Evaluation of Detection Capability for Clinical Laboratory Measurement Procedures
  - CLSI EP24-A2 - diagnostic accuracy / ROC curves
  - NCCLS C28-A2 - reference intervals
  - NCCLS EP5-A (1999) - precision performance
  - NCCLS EP5-A2 (2004) - precision performance
  - NCCLS EP6-A (2003) - linearity, weighted regression
  - NCCLS EP10-A2 - preliminary evaluation
  - NCCLS GP10-A - study planning

## Expert testimony
- [Expert testimony](https://www.johndcook.com/blog/expert-testimony/): Knowledge and experience to analyze and interpret data properly, professional credentials to be credible, and communication skills to convey the results to a non-technical audience.
- [Explaining probability to a jury](https://www.johndcook.com/blog/explaining-probability-to-a-jury/): Why it is difficult but necessary to explain probability to judges and jurors. Why John D. Cook has the skill and experience to do this.

## Background 
- PhD in applied mathematics from University of Texas at Austin
- Postdoc Vanderbilt University
- Researcher at University of Texas MD Anderson Cancer Center (MDACC) in the department of biostatistics
- Adjunct faculty at University of Texas Graduate School of Biomedical Sciences (UT GSBS)

## Publications

- [Journal articles and technical reports](https://www.johndcook.com/blog/articles/)  
  Peer-reviewed papers and technical reports on Bayesian statistics, adaptive clinical trials, stochastic inequality probabilities, numerical methods, and applied mathematics.

### Representative publications

- Bayesian Design of Single-Arm Phase II Clinical Trials with Continuous Monitoring (Clinical Trials, 2009)
- A Case for Robust Bayesian Priors with Applications to Binary Clinical Trials (Bayesian Analysis, 2009)
- Dose-finding based on efficacy-toxicity trade-offs (Biometrics, 2004)
- Stochastic Inequality Probabilities for Adaptively Randomized Clinical Trials (Biometrical Journal, 2006)
- High performance implementation of the hierarchical likelihood for generalized linear mixed models (BMC Medical Research Methodology, 2021)

## Common questions

- [What is HIPAA Safe Harbor?](https://www.johndcook.com/blog/hipaa-identifiers-explained/)
- [What is differential privacy?](https://www.johndcook.com/blog/differential-privacy/)
- [Does removing names and addresses make data deidentified?](https://www.johndcook.com/blog/dp1/)
- [Does HIPAA Safe Harbor actually protect privacy?](https://www.johndcook.com/blog/dp2/)
- [How effective are software packages at removing PII?](https://www.johndcook.com/blog/dp3/)
- [Why doesn't hashing protect privacy?](https://www.johndcook.com/blog/dp4/)
- [How do state privacy laws extend HIPAA?](https://www.johndcook.com/blog/dp5/)
- [What is pseudonymization?](https://www.johndcook.com/blog/dp6/)
- [What is a privacy incident?](https://www.johndcook.com/blog/dp7/)
- [What are some privacy metrics and techniques?](https://www.johndcook.com/blog/dp8/)
- [What are some privacy risks that are not obvious?](https://www.johndcook.com/blog/dp9/)