ModsFinder

SHA-1 Redemption

by exaptations

SHA-1 Redemption is a Java Agent and NilLoader utility for Minecraft 1.4.2 – 1.6.4 that works around SHA-1 signature checks in legacy Forge jars.

NilLoaderJava AgentClient or server, optionalMIT LicenseOpen source1.4.2 – 1.6.4

What it does

Older Minecraft releases and Forge builds were signed with SHA-1, an algorithm newer Java 8 releases no longer trust, so the game can refuse to start after a mod or the Minecraft jar is changed. This mod patches the JVM's signature handling so those checks pass again on the legacy versions it covers.

The author explains that the Forge loader's tamper detection is poorly implemented and triggers on jar changes it cannot judge. Users who instead want to restore a clean Minecraft jar, or add the -Dfml.ignoreInvalidMinecraftCertificates=true flag to the launcher profile, can do so without this mod, which the author documents as the other route. The mod is published as a Java Agent and as a NilLoader build, both for 1.6.4.

Environment: either side can run it, and neither needs it. The code is licensed under the MIT License and is open source; a source repository and an issue tracker are linked from the project page. Files cover 1.4.2, 1.4.4, 1.4.5, 1.4.6, 1.4.7, 1.5.1, 1.5.2, 1.6.1, 1.6.2 and 1.6.4, with 1.0 for 1.6.4 as the latest Java Agent file.

Key features

  1. Signature check bypass

    Lets legacy Forge and Minecraft jars load on Java releases that no longer trust SHA-1 signatures.

  2. Java Agent loading

    Installs as a Java Agent, attaching to the JVM at startup without replacing the game jar.

  3. NilLoader build

    A separate NilLoader package provides the same workaround through that loader.

Compatibility

Latest build for each game version and loader.

1.6.x3 of 3 versions with builds
1.6.41.0+slim1.0
1.6.21.0+slim1.0
1.6.11.0+slim1.0
1.5.x2 of 2 versions with builds
1.5.21.0+slim1.0
1.5.11.0+slim1.0
1.4.x5 of 5 versions with builds
1.4.71.0+slim1.0
1.4.61.0+slim1.0
1.4.51.0+slim1.0
1.4.41.0+slim1.0
1.4.21.0+slim1.0
ReleaseBetaAlphaNot available

Only full game releases are shown. This mod publishes no snapshot builds.

Use cases

Modpacks on old Forge

Packs that bundle jars modified before the mod existed can start without re-signing every file.

Jar-modded legacy clients

Players running edited Minecraft jars on 1.6.4 can keep them instead of restoring a clean copy.

Who it’s for: Players and modpack makers who run Minecraft 1.4.2 – 1.6.4 with Forge and jar-modified files, and who understand that the check being bypassed is a security measure.

Questions

Does SHA-1 Redemption need Forge installed?

The mod is a Java Agent or NilLoader package for 1.6.4 and works alongside the legacy Forge setup it targets. It does not install Forge by itself.

Which game versions does SHA-1 Redemption support?

Its files cover 1.4.2, 1.4.4, 1.4.5, 1.4.6, 1.4.7, 1.5.1, 1.5.2, 1.6.1, 1.6.2 and 1.6.4, the same range listed on the project page.

Must the server also run SHA-1 Redemption?

No. Either side can run it, and neither needs it. Installing it on the client is enough for the signature bypass to apply there.

In the catalog

SHA-1 Redemption is one of 36,990 Utility mods on ModsFinder. 328 mods support Minecraft 1.6.4.

Utility mods36,990Mods for 1.6.4328

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Similar mods

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What the author says

[SEVERE] [ForgeModLoader] The minecraft jar file:/home/una/.local/share/PrismLauncher/libraries/com/mojang/minecraft/1.6.4/minecraft-1.6.4-client.jar!/net/minecraft/client/ClientBrandRetriever.class appears to be corrupt! There has been CRITICAL TAMPERING WITH MINECRAFT, it is highly unlikely minecraft will work!…
exaptations, on the Modrinth page

Official listing

Owner
exaptations
Published
2025-06-17
Updated on Modrinth
2025-06-17
Facts verified
2026-10-15

Tags

UtilityMagic
Open on ModrinthCompare