All SolutionsAll Solutions
🔐
TOTP
Week 38, 2026
Test each secret, use valid to generate results | greenya | Odin Solutions
package main
import "core:fmt"
import "core:slice"
main :: proc () {
next_secret: for secret in 0..=255 {
fmt.printfln("Checking secret: %i", secret)
for test in ([?] [2] int {
{ 1785818743, 995543 },
{ 1785818761, 399222 },
{ 1785818823, 988976 },
}) {
if test[1] != otp_gen(test[0], secret) {
continue next_secret
}
}
fmt.println("Found! The result OTPs:")
for timestamp in ([?] int { 123456789, 1798156817, 1798761646 }) {
otp := otp_gen(timestamp, secret)
fmt.printfln("%i: %i", timestamp, otp)
}
break
}
}
otp_gen :: proc (timestamp: int, secret: int) -> int {
ts := timestamp / 30
buf: [32] u8
str := fmt.bprint(buf[:], ts)
slice.reverse(transmute ([] u8) str)
value := ts + secret
for c in str do if c != '0' do value *= int(c-'0')
for (value/10)*10 == value do value /= 10
return value%1000000
}
Test each secret, use valid to generate results | greenya | Odin Solutions
package main
import "core:fmt"
import "core:slice"
main :: proc () {
next_secret: for secret in 0..=255 {
fmt.printfln("Checking secret: %i", secret)
for test in ([?] [2] int {
{ 1785818743, 995543 },
{ 1785818761, 399222 },
{ 1785818823, 988976 },
}) {
if test[1] != otp_gen(test[0], secret) {
continue next_secret
}
}
fmt.println("Found! The result OTPs:")
for timestamp in ([?] int { 123456789, 1798156817, 1798761646 }) {
otp := otp_gen(timestamp, secret)
fmt.printfln("%i: %i", timestamp, otp)
}
break
}
}
otp_gen :: proc (timestamp: int, secret: int) -> int {
ts := timestamp / 30
buf: [32] u8
str := fmt.bprint(buf[:], ts)
slice.reverse(transmute ([] u8) str)
value := ts + secret
for c in str do if c != '0' do value *= int(c-'0')
for (value/10)*10 == value do value /= 10
return value%1000000
}
py | shallowspirit | Python Solutions
def gen_otp(timestamp, secret):
part1 = timestamp // 30
total = part1 + secret
digits = str(part1)[::-1]
for d in digits:
d = int(d)
if d == 0:
continue
total = d * total
s = str(total)
s = s.rstrip('0')
if s == '':
s = '0'
otp = s[-6:] if len(s) >= 6 else s.zfill(6)
return otp
# Known OTPs shoulder-surfed from the suspect's phone
targets = {
1785818743: "995543",
1785818761: "399222",
1785818823: "988976",
}
# Brute-force every possible 8-bit secret key (0-255)
for secret in range(256):
ok = True
for ts, expected in targets.items():
got = gen_otp(ts, secret)
if got != expected:
ok = False
break
if ok:
print("Found secret:", secret)
# Once found, generate OTPs for the required timestamps
secret = 38
for ts in [123456789, 1798156817, 1798761646]:
print(ts, gen_otp(ts, secret))
