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Time-based one-time password algorithm: Difference between revisions
Tcl implementation added
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oh dear... fall back one time-frame...
742249 is *that* the same? #t</pre>
=={{header|Tcl}}==
This TOTP/HOTP module clocks in small by taking advantage of [https://core.tcl.tk/tcllib/doc/trunk/embedded/www/toc.html tcllib's] existing hashing and base32 modules.
<lang Tcl>
# rfc6238 contains examples of hotp with 8-digit modulus and sha1/sha256/sha512 hmac
#
# these require options handling, perhaps http://wiki.tcl.tk/38965
#
catch {namespace delete ::totp}
namespace eval ::totp {
package require sha1
oo::class create totp {
variable Secret
variable Interval
variable Window
constructor {secret {interval 30} {window 300}} {
if {![string is digit $interval]} {
set interval [expr {[clock scan $interval] - [clock scan now]}]
}
if {![string is digit $window]} {
set window [expr {[clock scan $window] - [clock scan now]}]
}
if {$window % $interval} {
throw {TOTP BADARGS} "$window is not a multiple of $interval"
}
set window [expr {$window / $interval}]
set Secret $secret
set Interval $interval
set Window $window
}
method totp {{when now}} {
if {![string is integer $when]} {
set when [clock scan $when]
}
set when [expr {$when / $Interval}]
set bytes [binary format W $when]
binary scan $bytes H* when
hotp $Secret $bytes
}
}
proc hotp {secret bytes} {
set hmac [sha1::hmac -bin $secret $bytes]
set ofs [string index $hmac end]
binary scan $ofs c ofs
set ofs [expr {$ofs & 0xf}]
set chunk [string range $hmac $ofs $ofs+4]
binary scan $chunk I code
return [expr {($code & 0x7fffffff) % 1000000}]
}
namespace export *
}
namespace import ::totp::*
if 0 { ;# tests
if {[info commands assert] eq ""} {
proc assert {what} {
puts [uplevel 1 [list subst $what]]
}
}
totp::totp create t 12345678901234567890
assert {287082 eq [t totp 59]}
t destroy
package require base32
totp::totp create t [base32::decode AAAAAAAAAAAAAAAA]
proc google {when} {
list [t totp [expr {$when-30}]] [t totp $when] [t totp [expr {$when+30}]]
}
assert {{306281 553572 304383} eq [google 1400000000]}
}</lang>
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