How to Fix Git GPG Signing Error

In this tutorial, you'll learn about How to Fix Git GPG Signing Error. We cover key concepts, practical examples, and best practices.

You run git commit -S and get error: gpg failed to sign the data — Git cannot find your GPG key or the key is not configured correctly.

The Problem

error: gpg failed to sign the data
fatal: failed to write commit object

Or:

gpg: signing failed: No secret key

Step-by-Step Fix

Step 1: Check if you have a GPG key

gpg --list-secret-keys --keyid-format LONG

If no output, generate a new key.

Step 2: Generate a GPG key

gpg --full-generate-key

Select:

• Type: RSA and RSA (default)
• Size: 4096
• Expiry: 0 (no expiry)
• Email: must match your Git email

Step 3: List and copy your public key

gpg --list-secret-keys --keyid-format LONG

Copy the key ID (after rsa4096/):

sec   rsa4096/ABC123DEF456 2026-01-01 [SC]

Export the public key:

gpg --armor --export ABC123DEF456

Step 4: Configure Git to use the key

git config --global user.signingkey ABC123DEF456

Step 5: Enable commit signing globally

git config --global commit.gpgsign true

Step 6: Add the GPG key to GitHub/GitLab

1. Copy the public key output
2. Go to GitHub → Settings → SSH and GPG keys → New GPG key
3. Paste and save

Step 7: Test signing

git commit --allow-empty -S -m "Test GPG signing"

Step 8: Verify the signature

git log --show-signature -1

Expected:

commit abc1234...
Good "git" signature for user@example.com with RSA key ABC123DEF456

Prevention Tips

• Ensure your Git email matches the GPG key email exactly
• Enable commit signing globally
• Back up your GPG key and revocation certificate
• Use export GPG_TTY=$(tty) to fix signing in terminals
• Configure gpg-agent for passphrase caching

Common Mistakes with gpg signing

1. Overlapping type class instances that cause GHC to reject the program with ambiguous dispatch errors
2. Non-exhaustive pattern matches that compile with warnings then crash at runtime
3. Misunderstanding that String is [Char] with poor performance for large text operations

These mistakes appear frequently in real-world GIT code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

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