MAC - Managed Authentication&Crypto Service provides  
consumer-facing services enabling mobile phone as personal
transaction authorisation device (in use since 2000). This is how it
works : Consumer accessing MAC may request 2-factor authentication
 for low-value transaction or 3-factor authentication for high-value
transaction. 2-factor authentication includes mobile phone Caller ID
and PIN. 3-factor authentication includes in addition Live Voice
Biometrics.
Live Voice Biometrics based upon SentryCom
proprietary and patented technology precludes
tape-record-and- playback attack.
Solutions : Mobile Phone as
Transaction Authorisation Device.
Consumer may attach this code
to any transaction he chooses.
For example :
ATM withdrawal
personal check
point-of-sale transaction
online transaction.
The merchant receiving such a
transaction may validate TAC vs.
MAC service.
TAC serves as  electronic
signature.
The e-signature bill specifies
that in the United States, the use
of a electronic  signature is as
legally valid as a traditional
signature written in ink on paper.
On success - consumer will
receive 6 digit Transaction
Authorisation Code (TAC)..