Changes between Version 96 and Version 97 of FAQ

Timestamp:

2013-07-29T10:28:31Z (11 years ago)

Author:

daira

Comment:

describe the difference between erasure coding and secret sharing

FAQ

@@ -21 +21 @@
 The default Tahoe-LAFS parameters are {{{3-of-10}}}, so the data is spread over 10 different drives, and you can lose any 7 of them and still recover the entire data.  This gives much better reliability than comparable RAID setups, at a cost of only 3.3 times the storage space that a single copy takes.  It takes about 3.3 times the storage space, because it uses space on each server equal to 1/3 of the size of the data, and there are 10 servers.
 
-Erasure coding is also known as "forward error correction".
+"Forward error correction" is another term for erasure coding.
+
+Erasure coding should not be confused with "secret sharing", which has the additional security property that fewer than {{{K}}} servers cannot recover any information about the data. Tahoe-LAFS' erasure coding does not have this property, and does not need to have it because we rely on secret-key encryption (using a key in the read cap) for confidentiality.
+
+"Information Dispersal Code" (IDA) can refer either to an erasure code or a secret sharing algorithm depending on context, so we prefer not to use that term.
 
 '''[=#Q3_disable_encryption Q3:] Is there a way to disable the encryption for content which isn't secret? Won't that save a lot of CPU cycles?'''