---
id: "kerione-secure-privacy-authenticity-and-confidentiality-spac"
type: "paper"
type_label: "Papers and paper collections"
title: "Secure Privacy, Authenticity, and Confidentiality (SPAC)"
maintainer: "Samuel M. Smith, Ph.D."
authors:
  - "Samuel M. Smith, Ph.D."
date: "2023-03-25"
year: 2023
reading_level: "implementer"
reading_level_label: "Implementer"
reading_level_meaning: "developers working in or against the code"
evidence: "informative"
evidence_meaning: "an author's paper, deck, tutorial or post explaining the suite"
status: "active"
status_meaning: "changed within the last six months, or a live service"
access: "public"
access_meaning: "anyone with the link"
topics:
  - "theory"
  - "cryptography"
  - "specifications"
roles:
  - "developer"
  - "security-architect"
  - "standards-policy"
  - "researcher"
source_url: "https://github.com/SmithSamuelM/Papers/blob/master/whitepapers/SPAC_Message.md"
source_license: null
source_license_note: null
found_on: "keri-one-resources"
kerisse_credit: false
abstract_license: "CC BY 4.0"
abstract_license_url: "https://creativecommons.org/licenses/by/4.0/"
abstract_attribution: "KSKB, the KERISuite Knowledge Base (https://kskb.dev/)"
last_checked: "2026-10-14"
kskb_url: "https://kskb.dev/cards/kerione-secure-privacy-authenticity-and-confidentiality-spac/"
kskb_app_url: "https://kskb.dev/#item/kerione-secure-privacy-authenticity-and-confidentiality-spac"
kskb_record_url: "https://kskb.dev/data/kskb/resources/kerione-secure-privacy-authenticity-and-confidentiality-spac"
kskb_markdown_url: "https://kskb.dev/export/cards/kerione-secure-privacy-authenticity-and-confidentiality-spac.md"
---

# Secure Privacy, Authenticity, and Confidentiality (SPAC)

A white paper, in Markdown on GitHub, that sets out the PAC (privacy, authenticity, confidentiality) trilemma and designs messaging protocols that give the best privacy possible given the strongest authenticity and confidentiality, using KERI autonomic identifiers and a modified ESSR (Encrypt Sender, Sign Receiver) construction. It covers threat models, relationship formation, intermediaries, interaction contexts and a CESR encoding, and is aimed at protocol designers.

Labels: reading level Implementer; evidence informative (an author's paper, deck, tutorial or post explaining the suite).
Source: https://github.com/SmithSamuelM/Papers/blob/master/whitepapers/SPAC_Message.md (license not recorded).
The abstract is KSKB's own text under Creative Commons Attribution 4.0 (CC BY 4.0), https://creativecommons.org/licenses/by/4.0/; credit KSKB, the KERISuite Knowledge Base (https://kskb.dev/).