[messaging] Password reset mechanisms with an SRP authentication framework

[Michael Rogers]

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On 22/04/14 19:47, Trevor Perrin wrote:
>> * The friends don't have enough shares to reconstruct the key
>> even if they collude
> 
> They do, if n-2 >= k.

Doh, sorry, I tried to generalise this from k=4, n=5 and failed. :0)
The user should keep n-k+1 shares on her device.

> I would assume you know your friends' public keys, do a k-of-n
> share of a symmetric key used to encrypt the backup data, then
> encrypt each share under one of the public keys.  Then store all
> ciphertext in a backup file you widely distribute (containing both
> the encrypted shares and encrypted backup data).
> 
> The nice thing about this is you can use your friends for backup 
> without ever contacting them, except in the event of recovery.

Nice!

Cheers,
Michael
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