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The cryptocurrency Nextcoin has users create Curve25519 signing keys with a minimum length of 70 characters.

Is that secure? Would it be better to use a random number generator? Is it possible to quantify how much better?

(If this should be on bitcoin.se, I understand, but I'm only interested in Curve25519 signing key security not the cryptocurrency functionality.)

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Deriving keys from a password is completely unrelated to Curve25519 itself. The main security risk is the user choosing a bad passphrase. –  CodesInChaos Jan 12 at 16:11
@CodesInChaos Thank you again CodesInChaos! I will assume from your answer that a RNG is far more secure. Thank you so much again! –  Cincinnatus Jan 12 at 16:14

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