Armory Devs: Can I safely make public my SecurePrint paper backup?

goatpig

legendary

Activity: 3766

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Armory Developer

Quote from: pf on September 27, 2015, 10:01:45 AM

This is a more secure alternative, right? Because with SecurePrint, if an attacker has the SecurePrint paper backup but not the SecurePrint code, he can still try to brute-force it. On the other hand, with the 2/2 fragmented backup, if the attacker gets only one of them, he can't even do anything. There's nothing he can brute force. Am I right? Or is there actually something he can brute force but it's just way more expensive than the SecurePrint brute force?

Look up on Shamir Secret Sharing to understand the security behind fragmented backups. If you use SecurePrint fragmented backups, then the attacker really has nothing. Keep in mind the SecurePrint passphrase is unique per wallet, i.e. there's only one SP passphrase for any N fragments.

pf

full member

Activity: 176

Merit: 105

Quote from: goatpig on September 27, 2015, 06:47:18 AM

https://bitcointalksearch.org/topic/m.11912743

TLDR: If you don't like the security of SecurePrint, use fragmented backups.

Thanks for reminding me.

I guess you're right. I could simply create a 2-2 fragmented backup. Print out one. Write the other down manually. In other words:

Instead of:
SecurePrint paper backup + SecurePrint code
I'd have:
1st fragment printed + 2nd fragment written down

This is a more secure alternative, right? Because with SecurePrint, if an attacker has the SecurePrint paper backup but not the SecurePrint code, he can still try to brute-force it. On the other hand, with the 2/2 fragmented backup, if the attacker gets only one of them, he can't even do anything. There's nothing he can brute force. Am I right? Or is there actually something he can brute force but it's just way more expensive than the SecurePrint brute force?

goatpig

legendary

Activity: 3766

Merit: 1364

Armory Developer

https://bitcointalksearch.org/topic/m.11912743

TLDR: If you don't like the security of SecurePrint, use fragmented backups.

pf

full member

Activity: 176

Merit: 105

It's a simple question that I kinda need answered:

Can I safely make public my SecurePrint paper backup?

If this is not the case, I really don't see the point of SecurePrint. Reason: The whole point of SecurePrint is to guard against the risk that the printed backup leaks to someone else. (That's why you write down the SecurePrint code on the paper after printing it.) That someone else could leak it public.

So without an affirmative answer to the above question, SecurePrint is pointless.

Topic: Armory Devs: Can I safely make public my SecurePrint paper backup? (Read 615 times)