The disclosure provides a method of updating time in a transaction between a transaction device and an offline terminal. Firstly, a transaction is initiated (401) between a transaction device and an offline terminal. A stored trusted time value is then provided and another trusted time value received (402). Each trusted time value exchanged has been affirmed by a trusted time provider. The obtained trusted time value is then compared (404) with the stored trusted time value. The stored trusted time value is replaced (405) with the obtained trusted time value if the obtained trusted time value is more recent than the stored trusted time value. The method may be implemented in a transaction device or a terminal, and methods of risk management in a transaction device and a terminal are also described. Suitably programmed transaction devices and terminals are also described, as is a trusted time provider for a transaction system.
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