SAFU Ninja
The Safu Ninja is a ultra-durable mnemonic backup system built from off-the-shelf stainless steel components. It allows you to permanently imprint your recovery words (and their order index) onto steel washers, then stack them into a tamper-resistant assembly. Because it uses components that aren’t explicitly designed for cryptocurrency, it preserves your privacy—no “Bitcoin backup” branding to attract unwanted attention.
What You Get
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Stainless steel fender washers (size matched to your bolt)
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Stainless steel button/hex head bolt
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Stainless steel cap nut / wing nut
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Alignment jig for neat, consistent stamping
- Punch set
How It Works
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Stamp your mnemonic words — Each washer is stamped with one word from your recovery phrase (recommend stamping the full word, not just first 4 letters).
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Number the position — On each washer, also stamp the index (e.g. “03”) to preserve the order in case washers shift.
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Stack washers on the bolt — Thread them in correct sequence.
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Secure with nut — Tighten the nut to lock the washers in place.
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Seal or store — Place the assembled stack in a corrosion-resistant container, low-moisture environment, or bury it in a secure location.