Password Entropy The entropy bits of a password (also known as guess entropy), i.e., the information entropy of a password, measured in bits,is The base-2 logarithm of the number of guesses needed to find the password with certainty A password with, say, 42 bits of strength calculated in this way would be as strong as a string of 42 bits chosen randomly Adding one bit of entropy to a password doubles the number of guesses required 37Password Entropy • The entropy bits of a password (also known as guess entropy), i.e., the information entropy of a password, measured in bits, is • The base-2 logarithm of the number of guesses needed to find the password with certainty • A password with, say, 42 bits of strength calculated in this way would be as strong as a string of 42 bits chosen randomly • Adding one bit of entropy to a password doubles the number of guesses required Topic 3: User Authentication 372/3/2021