Cardano (ADA)

"Don't roll your own crypto" is the most repeated rule in all of security. SecondFi rolled their own, and brought back the oldest mistake in cryptography on the one algorithm designed to make it impossible.

Every signature needs a secret number used exactly once, called a nonce. get it even slightly wrong, reuse it, bias it, leak a few bits, and anyone can run the math backwards and rebuild your private key from public data. this exact bug cracked the PlayStation 3 and emptied early Bitcoin wallets more than a decade ago.

So cryptographers fixed it for good. Ed25519, the scheme Cardano uses, generates that nonce for you, deterministically, from your key and the message. there is no random number left for a developer to fumble. that safety is most of the reason it won. SecondFi wrote their own signer anyway, and fumbled the one thing you are not supposed to be able to fumble. their version bled a little of the key into every signature.

Which means your own transaction history, sitting permanently on a publi

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