The crib-drag attack applies with a different operator. p1 = AtextencryptedByFirstPassword p = HelloHelloHelloHelloHelloHell c1 = hxpihlrncmwxpopfjtcgatldgdsco p2 = ASecondEncryptedTextBySecondPassword p = HelloHelloHelloHelloHelloHelloHelloH c2 = hwpncuhpyqycaeskxpihicdpqvroaozwhzfk When you $c_1 - c_2 \bmod 26$ you will have the same problem as many-time-pad. This subtraction will remove the key. c1[i] - c2[i] = p1[i] - p2[i] But this time instead of $\oplus$ we will have plus modulo 26. c1 - c2 = azafvjqcwecflqdfowgbijsmkszmm