VeriLog

VeriLog is a cryptographically verifiable, tamper-evident audit logging library currently only for Java. A .NET equivalent plan is in breakdown.

It provides:

• Hash-chained audit entries
• ECDSA signatures (P-256)
• Framed binary log format
• Authenticated encryption (XChaCha20-Poly1305)
• Log rotation support
• End-to-end verification

VeriLog is designed for systems that require strong integrity guarantees, such as:

• Security-sensitive applications
• Compliance logging
• Financial systems
• Infrastructure audit trails
• High-assurance backends

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Why VeriLog?

Traditional logs can be:

• Edited retroactively
• Reordered
• Truncated
• Forged

VeriLog prevents this by combining:

Hash chaining

Each entry references the hash of the previous entry.

If one entry changes → the entire chain breaks.

Digital signatures

Each entry is signed using ECDSA (P-256).

You can cryptographically prove:

• Who created the entry
• That it has not been modified

Authenticated encryption

Log files are encrypted using XChaCha20-Poly1305.

This ensures:

• Confidentiality
• Integrity
• Tamper detection at file level

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Architecture Overview

Application
    ↓
SignedEntryFactory
    ↓
HashChainState
    ↓
FramedLogFile
    ↓
XChaCha20-Poly1305
    ↓
Disk

Each layer enforces a specific security property:

Layer	Guarantees
Hash chain	Forward integrity
ECDSA signature	Authenticity
AEAD encryption	Confidentiality + integrity
Framing	Structural validation

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Example (High-Level)

VeriLogger logger = VeriLogger.builder()
    .logDir(Path.of("logs"))
    .encryptionKey(key32Bytes)
    .signer(signer)
    .build();

logger.log("user.login", Map.of(
    "userId", "1234",
    "ip", "10.0.0.5"
));

Later:

VeriLogReader.verifyDirectory(Path.of("logs"));

If anything was modified, verification fails.

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Security Model

VeriLog assumes:

• The signing key is protected.
• The encryption key is protected.
• Attackers may have read/write access to log files.
• Attackers may attempt to:
  • Modify entries
  • Remove entries
  • Insert fake entries
  • Reorder entries

VeriLog guarantees detection of such tampering.

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Status

! Early stage. APIs may change until 1.0.0.

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License

Copyright 2026 Erik Marten

This project is licensed under the Apache License 2.0.

You may use, modify, and distribute this software in accordance with the License. A copy of the License is provided in the LICENSE file.

This software provides cryptographic functionality. Users are responsible for ensuring compliance with all applicable laws and regulations regarding the use, distribution, and export of cryptographic software.

Distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND.