audit_log_cipher.h File Reference

At-rest encryption for ATNA audit log records (ISO 27799 compliance) More...

#include "kcenon/pacs/core/result.h"
#include <array>
#include <cstddef>
#include <cstdint>
#include <mutex>
#include <string>
#include <unordered_map>
#include <vector>

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Classes
struct	kcenon::pacs::security::audit_cipher_key
	A versioned symmetric key pair (data encryption + MAC) More...
class	kcenon::pacs::security::audit_key_manager
	Holds the active encryption key and any retired keys for decryption of historical records. More...
class	kcenon::pacs::security::audit_log_cipher
	Encrypts and decrypts single audit log records. More...

Namespaces
namespace	kcenon
namespace	kcenon::pacs
namespace	kcenon::pacs::security
namespace	kcenon::pacs::security::detail

Functions
std::string	kcenon::pacs::security::detail::base64_encode (const std::uint8_t *data, std::size_t size)
	Standard base64 encode (no line breaks)
bool	kcenon::pacs::security::detail::base64_decode (const std::string &in, std::vector< std::uint8_t > &out)
	Standard base64 decode; returns false on malformed input.
bool	kcenon::pacs::security::detail::hex_decode (const std::string &in, std::uint8_t *out, std::size_t out_size)
	Hex decode (lowercase or uppercase); returns false on malformed input.
bool	kcenon::pacs::security::detail::constant_time_equal (const std::uint8_t *a, const std::uint8_t *b, std::size_t n) noexcept
	Constant-time equality on byte buffers of equal length.

Variables
constexpr const char *	kcenon::pacs::security::audit_cipher_format_tag = "PACSAUDIT"
	Format version string embedded in every encrypted record.
constexpr const char *	kcenon::pacs::security::audit_cipher_format_version = "v1"
constexpr std::size_t	kcenon::pacs::security::audit_cipher_key_bytes = 32
	AES-256 key length in bytes.
constexpr std::size_t	kcenon::pacs::security::audit_cipher_mac_key_bytes = 32
	HMAC-SHA256 key length in bytes (equal to block size for full strength)
constexpr std::size_t	kcenon::pacs::security::audit_cipher_iv_bytes = 12
	GCM IV length in bytes (NIST SP 800-38D recommended 96 bits)
constexpr std::size_t	kcenon::pacs::security::audit_cipher_tag_bytes = 16
	GCM authentication tag length in bytes.

Detailed Description

At-rest encryption for ATNA audit log records (ISO 27799 compliance)

Provides AES-256-GCM authenticated encryption with HMAC-SHA256 integrity signing for audit log records. Supports key rotation by embedding a key identifier in every record so that historical records remain decryptable after rotation.

Record format (ASCII, single line, terminated by '
'):

*   PACSAUDIT|v1|<key_id>|<iv_b64>|<ciphertext_b64>|<tag_b64>|<hmac_b64>
* 

Where:

• v1 is the format version tag
• key_id is the identifier of the key used to encrypt the record
• iv_b64 is the 96-bit AES-GCM initialisation vector (base64)
• ciphertext_b64 is the AES-256-GCM ciphertext (base64)
• tag_b64 is the 128-bit AES-GCM authentication tag (base64)
• hmac_b64 is an HMAC-SHA256 over the preceding fields (base64), bound to a separate MAC key for defence-in-depth per ISO 27799 §7.9

See also

ISO 27799:2016 §7.9 — Audit logging (integrity & confidentiality)

HIPAA §164.312(b) — Audit controls

Issue #1102

Author

kcenon

Since

1.0.0

Definition in file audit_log_cipher.h.