These are the transaction authentication numbers which are unique for each new transaction: https://en.m.wikipedia.org/wiki/Transaction_authentication_number h

These are the transaction authentication numbers which are unique for each new transaction: https://en.m.wikipedia.org/wiki/Transaction_authentication_number https://en.m.wikipedia.org/wiki/Transaction_authentication_n... For me in the UK to move money I need to generate a TAN using a SecureID token the TAN is generated by using the secret in the token and digits of the account number I need to transfer money too. The same SecureID also generates OTP for 2FA login. But there are other TAN schemes including pregenerated lists and TANs sent over SMS or TANs which are generated by using the smartcard in your debit card.