Password Difficulties

Bruce Schneier schneier at chinet.chinet.com
Sat Jul 2 14:44:18 PDT 1994


Figure that each English character has 1.8 bits of entropy.  (This is
a conservative number, because it doesn't take into account case, spacing,
or punctuation.)  If I want a passphrase that will map into a 64-bit 
keyspace, I need at least a 35-chararcter phrase.

I generally assume that I need about one word per byte of key.  Thus, if
I want to generate a 64-bit key, I need an eight-word phrase.

Bruce





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