Check mapping: t→t, h→h, m→e? No. Fails.
But ROT-(-3): F(-3)=C, S(-3)=P, B(-3)=Y → CPY no. thmyl fys bwk andrwyd 5.1.1
thmyl fys bwk andrwyd 5.1.1 → their fsb backdoor andrwyd 5.1.1 Check mapping: t→t, h→h, m→e
However, "andrwyd" = android if: a→a, n→n, d→d, r→r, w→o? w→o is left one key on QWERTY (w left is q? no). w right is e? not o. So maybe : Check mapping: t→t
However, if fys is FSB with ROT-3: F(+3)=I, S(+3)=V, B(+3)=E → IVE no.
Wait — known trick: fys = fsb if y→s is shift -6, but b unchanged. Unlikely.