Excel Password Recovery by Version

At-a-Glance Comparison

Speeds above are per high-end consumer GPU (RTX 4090 class) for dictionary and mask attacks. A 6-GPU cluster scales roughly linearly.

Why Excel 97-2003 Is Always Recoverable

Microsoft released Excel 97 in 1996. Back then, US export regulations restricted strong cryptography, so Microsoft shipped Excel with a deliberately weak 40-bit RC4 cipher. A 40-bit key has roughly one trillion (2^40) possible values. On a modern GPU, you can try all one trillion keys in a few hours. Recovery does not even involve passwords — the service searches the key space directly and decrypts the file once the correct key is found.

That means every password-protected .xls from Excel 97, 2000, XP or 2003 is mathematically recoverable, whether the password is "1234" or 60 characters of random binary. This is what makes our guaranteed recovery offering possible.

The 2007 Generational Leap

Excel 2007 introduced the .xlsx format — an XML-based Office Open XML container — and replaced 40-bit RC4 with real AES-128. Instead of searching a one-trillion-key space, an attacker now has to guess the original password and derive the key from it using SHA-1 at 50,000 iterations.

50,000 rounds of SHA-1 on a GPU is still cheap — about 1.5 million candidates per second per RTX-class GPU. That sounds fast, but set against passwords of realistic length it is still the dominant time cost. A dictionary of 14 billion leaked passwords runs in about 2.5 hours on a single GPU for 2007 files; on six GPUs in parallel, roughly 25 minutes.

The 2010 Hardening — 10x Slower Attacks

Excel 2010 switched from SHA-1 to SHA-512 and doubled iterations to 100,000. Per-GPU attack speed drops from ~1.5 million to ~140,000 candidates per second — a 10x slowdown. A 14-billion-entry dictionary now takes roughly 28 hours on a single GPU. Still feasible in a cluster, but the scope of attacks shifts from "try everything" to "try targeted wordlists and masks".

2013 and Later — Same Spec, Stronger Reality

From a pure cryptography standpoint, Excel 2013, 2016, 2019 and Microsoft 365 are identical: AES-128 with SHA-512 at 100,000 iterations. Microsoft did not bump iteration count again because the attack ecosystem shifted: modern GPUs still churn through 140k/s, so adding iterations would have hurt honest users (slow file open) without stopping motivated attackers.

So why are odds progressively worse? Three reasons:

• Password managers became mainstream. Excel 2007 files are often from an era when people typed pet names. Excel 2019 files are more likely protected with a 16-character random string from a password manager.
• UI nudges toward stronger passwords. Newer Excel versions show real-time strength meters, complain about short passwords, and default to stricter policies in corporate deployments.
• User awareness. High-profile data breaches of the last decade trained business users to use unique passwords they do not reuse.

What About Sheet Protection?

None of the encryption above applies to Excel sheet protection, which is a soft lock stored as XML. Sheet protection can be removed in minutes without any password — see our step-by-step unprotect Excel sheet guide. This page is specifically about the file-open password that Excel requires before it displays anything.

How to Tell Which Version Saved Your File

Three quick checks, in order of reliability:

1. Extension — .xls means Excel 97-2003 regardless of when you think the file was created. .xlsx means Excel 2007 or later.
2. Encryption header — open the file in a hex editor. Excel 97-2003 files start with D0 CF 11 E0 (OLE compound). Excel 2007+ .xlsx files start with 50 4B 03 04 (ZIP). An encrypted .xlsx is wrapped in an OLE container so it also shows D0 CF 11 E0 — unzip-like tools will refuse.
3. Internal version string — for unencrypted .xlsx, the app name lives in docProps/app.xml. For encrypted files you need a dedicated parser; recovery services detect this automatically on upload.

Realistic Outcomes — Three User Examples

Frequently Asked Questions