Why Archive Integrity Matters
Imagine you need to prove in court exactly what your website displayed on a specific date. You have an archive. You present it as evidence. The opposing counsel asks a simple question: “How do we know this archive has not been modified since it was created?”
If you cannot answer that question with technical certainty, your archive loses much of its evidentiary value. A web archive without integrity verification is a document that could have been altered at any point between capture and presentation. It might be perfectly accurate. But “might be” is not the standard that courts, regulators, and legal teams require.
This is why cryptographic verification exists in website archiving. It transforms an archive from a copy that someone claims is authentic into a record that can be mathematically proven to be unchanged since the moment of capture.
What Cryptographic Hashing Does
At its core, a cryptographic hash function takes any piece of digital data – a web page, an image, a PDF, an entire WARC file – and produces a fixed-length string of characters called a hash value, hash digest, or simply a hash. You can think of it as a digital fingerprint.
This fingerprint has several remarkable properties:
Deterministic. The same input always produces the same hash. If you run the same web page through the same hash function today, tomorrow, and ten years from now, you will always get the identical result.
Unique. Even the smallest change to the input produces a completely different hash. Change a single character in a million-character document, and the resulting hash will be entirely different. This property is what makes hashing so powerful for tamper detection.
One-way. You cannot reverse a hash to reconstruct the original data. The hash proves that the original data has not changed, but it does not expose the data itself. This is important for situations where the hash may be shared or stored separately from the archived content.
Fixed-length. Regardless of whether the input is a 500-byte HTML page or a 5-gigabyte WARC file, the hash is always the same length. A SHA-512 hash is always 128 hexadecimal characters. This makes hashes easy to store, compare, and transmit.
SHA-512 Explained
SHA-512 is a member of the SHA-2 (Secure Hash Algorithm 2) family, designed by the United States National Security Agency and published by the National Institute of Standards and Technology (NIST). The “512” refers to the length of the hash output in bits – 512 bits, which is expressed as 128 hexadecimal characters.
To put the security of SHA-512 in perspective: the number of possible SHA-512 hash values is 2 to the power of 512. That is a number with 155 digits. There are estimated to be roughly 10 to the power of 80 atoms in the observable universe. The number of possible SHA-512 hashes is incomprehensibly larger than the number of atoms in existence. Finding two different inputs that produce the same SHA-512 hash (a “collision”) is, for all practical purposes, impossible with current or foreseeable technology.
SHA-512 is widely used in government, financial services, and legal contexts. It is approved by NIST for use in protecting sensitive information and is recognised as a standard hash function in jurisdictions worldwide.
RIPEMD-160 Explained
RIPEMD-160 (RACE Integrity Primitives Evaluation Message Digest) is a cryptographic hash function developed in Europe by researchers at Katholieke Universiteit Leuven in Belgium. It produces a 160-bit (40 hexadecimal character) hash value.
RIPEMD-160 was designed independently of the SHA family, using a different mathematical approach. It has been extensively studied by the cryptographic community and remains secure against known attacks. Its European origin and independent development make it a valuable complement to the American-designed SHA-512.
Why Two Algorithms?
Using two independent cryptographic hash algorithms – SHA-512 and RIPEMD-160 – rather than one provides an additional layer of security through algorithmic diversity.
If a theoretical vulnerability were ever discovered in one algorithm (as happened with the older MD5 and SHA-1 algorithms), the second algorithm would still protect the archive’s integrity. The probability of both algorithms being compromised simultaneously, in a way that allows undetectable modification of archived data, is negligible.
This dual-algorithm approach follows a well-established security principle: defence in depth. Just as a building might have both a lock and an alarm system, using two independent hash functions ensures that the integrity of the archive does not depend on the security of any single algorithm.
How Tamper-Evident Archives Work
When Aleph Archives captures a website, the process of creating a tamper-evident record works as follows:
Step 1: Capture. Our browser-based archiving system renders and captures each page of the website, recording the complete HTTP request-response transaction, all associated resources, and comprehensive metadata. The capture is stored in an ISO 28500-compliant WARC file.
Step 2: Hashing. Immediately after capture, our system computes both a SHA-512 hash and a RIPEMD-160 hash for every archived resource. These hashes are recorded and associated with the archived content.
Step 3: Storage. The WARC file and its associated hash values are written to WORM storage (explained below). Once written, neither the archived content nor the hash values can be modified.
Step 4: Verification. At any point in the future – days, months, or years after capture – the integrity of any archived resource can be verified by recomputing its hashes and comparing them to the stored values. If the hashes match, the content is provably unchanged. If they do not match, tampering has occurred.
This process creates a mathematical proof of integrity. The hash values computed at the time of capture serve as an immutable reference point. Any alteration to the archived content, no matter how small, would produce different hash values, immediately exposing the modification.
WORM Storage: Physical Protection
Cryptographic hashing provides mathematical proof that content has not been altered. WORM storage provides physical protection to ensure it cannot be altered.
WORM stands for Write Once Read Many. It is a storage technology that allows data to be written a single time and then read any number of times, but never modified or deleted. Once a WARC file and its cryptographic hashes are written to WORM storage, they are physically protected against alteration.
WORM storage is not a software feature that can be overridden by an administrator with the right password. It is a fundamental property of the storage medium or the storage system’s firmware. The data cannot be changed because the storage system will not permit write operations to occupied sectors.
This technology is well-established in regulated industries. SEC Rule 17a-4, which governs records retention for broker-dealers, specifically requires that electronic records be preserved in a “non-rewritable, non-erasable format” – which is precisely what WORM storage provides. The combination of WORM storage with cryptographic verification creates a dual-layered protection system: the hashes prove the content is unchanged, and the storage ensures it cannot be changed.
Chain of Custody: From Capture to Courtroom
In legal contexts, evidence must have a documented chain of custody: an unbroken record of who controlled the evidence, how it was stored, and what protections were in place at every stage. A gap in the chain of custody can render evidence inadmissible.
For website archives, the chain of custody begins at the moment of capture and extends through storage, retrieval, and presentation:
Capture – The archiving system records what was captured, when, from which URLs, using which technology, and under what configuration. This metadata is part of the archive.
Hashing – Cryptographic hashes are computed immediately after capture, creating a verifiable baseline for the content’s integrity.
Storage – The archive is written to WORM storage with access controls and audit logging. Every access to the archive is recorded.
Retrieval – When the archive is needed, its integrity is verified by recomputing the cryptographic hashes and comparing them to the stored values. This verification confirms that the retrieved content is identical to what was originally captured.
Presentation – The verified archive can be presented as evidence with a complete, documented history of how it was captured, stored, and protected from alteration.
This chain of custody documentation, combined with cryptographic verification and WORM storage, creates archives that meet the highest evidentiary standards. The archive is not just a copy of a website. It is a forensically sound record with mathematical proof of its authenticity.
What This Means in Practice
For organisations in regulated industries, cryptographic verification is not an optional enhancement. It is the difference between an archive that serves as admissible evidence and one that can be challenged and dismissed.
Consider a pharmaceutical company that must prove its website displayed specific drug safety information on a certain date. With a cryptographically verified archive, the company can present the archived page along with its hash values, demonstrate that the hashes computed today match those recorded at the time of capture, and establish through WORM storage logs that the archive has been continuously protected from modification. This constitutes strong evidence that the archived content is exactly what appeared on the website.
Without cryptographic verification, the same company can only present a copy of a web page and assert that it is accurate. The opposing party can argue that the copy may have been modified, and there is no mathematical proof to refute that argument.
How Aleph Archives Implements Cryptographic Verification
At Aleph Archives, cryptographic verification is not an add-on feature. It has been a core element of our archiving platform since we were founded in 2010.
Every website archive we produce includes:
- SHA-512 hashes for every archived resource, computed at the moment of capture
- RIPEMD-160 hashes as an independent second verification layer
- WORM storage that physically prevents post-capture modification
- Complete metadata documenting the capture process, timestamps, and system configuration
- Audit logging that records every access to the archived content
This approach ensures that our clients’ archives are not merely copies of their websites. They are cryptographically verified, tamper-evident records that can withstand legal scrutiny. When a Fortune 500 client like Bombardier, Procter and Gamble, or Toyota needs to demonstrate what their website showed on a specific date, our archives provide evidence that meets the most demanding evidentiary standards.
The Foundation of Trust
A website archive without cryptographic verification requires trust: trust that the archiving provider did not modify the content, trust that no one with storage access altered the files, trust that the archive accurately represents what was captured. Trust is valuable, but it is not evidence.
Cryptographic verification replaces trust with proof. It transforms “we believe this archive is authentic” into “we can mathematically demonstrate this archive is unchanged since capture.” In legal, regulatory, and compliance contexts, that distinction is everything.
If your current website archives lack cryptographic verification, contact us to learn how Aleph Archives can provide the level of integrity your organisation requires.
