[cryptography] Oddity in common bcrypt implementation

Steven Bellovin smb at cs.columbia.edu
Tue Jun 28 13:05:04 EDT 2011

On Jun 28, 2011, at 11:36 42AM, Ian G wrote:

> On 28/06/11 11:25 AM, Nico Williams wrote:
>> On Tue, Jun 28, 2011 at 9:56 AM, Marsh Ray<marsh at extendedsubset.com>  wrote:
>>> Consequently, we can hardly blame users for not using special characters in
>>> their passwords.
>> The most immediate problem for many users w.r.t. non-ASCII in
>> passwords is not the likelihood of interop problems but the
>> heterogeneity of input methods and input method selection in login
>> screens, password input fields in apps and browsers, and so on, as
>> well as the fact that they can't see the password they are typing to
>> confirm that the input method is working correctly.
> This particular security idea came from terminal laboratories in the 1970s and 1980s where annoying folk would look over your shoulder to read your password as you typed it.
> The assumption of people looking over your shoulder is well past its use-by date.  These days we work with laptops, etc, which all work to a more private setting.  Even Internet Cafes have their privacy shields between booths.
> There are still some lesser circumstances where this is an issue (using your laptop in a crowded place or typing a PIN onto a reader/ATM). Indeed in the latter case, the threat is a camera that picks up the keys as they are typed.
> But for the most part, we should be deprecating the practice at its mandated level and exploring optional or open methods.  Like:
>> Oddly enough
>> mobiles are ahead of other systems here in that they show the user the
>> *last/current* character of any passwords they are entering.
As someone who regularly types a sensitive password with students looking
over his shoulder -- when my advisees come to visit, I often log on to a
web site to check their records -- I'd be unhappy to see this go away.

See Schneier's discussion at http://www.schneier.com/blog/archives/2009/07/the_pros_and_co.html

Btw -- the real issue in the 1960s (not the 1970s) was not the people around 
you -- the amount of personal space required to do work hasn't increased since
then, and may have decreased -- but the prevalence of hard-copy terminals,
since you'd be required to shred your printout to maintain security...
Some systems would print several different "dense" characters in the password
area; others, if they could, did turn off echo.  And if neither choice was 
available -- well, when using terminals based on Selectric typewriters, people 
would just pop off the type ball.

		--Steve Bellovin, https://www.cs.columbia.edu/~smb

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