1. A non-transitory computer-readable medium storing instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising: obtaining, at a client device, a credential identifier for a credential that is associated with a user; periodically, at a predetermined time period: obtaining, at the client device, a time derived from a timing device of the client device; determining, at the client device, at least one index value using the credential identifier and the time derived from the timing device of the client device; accessing, at the client device, a predetermined set of associations between index values and words; generating, at the client device, a phrase corresponding to the credential, the phrase being generated to include words that are associated with the at least one index value in the predetermined set of associations; receiving, at the client device, a user command to output the phrase; and responsive to the user command, rendering, at the client device, the phrase corresponding to the credential.
1. A non-transitory computer-readable medium storing instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising: obtaining, at a client device, a credential identifier for a credential that is associated with a user; periodically, at a predetermined time period: obtaining, at the client device, a time derived from a timing device of the client device; determining, at the client device, at least one index value using the credential identifier and the time derived from the timing device of the client device; accessing, at the client device, a predetermined set of associations between index values and words; generating, at the client device, a phrase corresponding to the credential, the phrase being generated to include words that are associated with the at least one index value in the predetermined set of associations; receiving, at the client device, a user command to output the phrase; and responsive to the user command, rendering, at the client device, the phrase corresponding to the credential. 3. The non-transitory computer-readable medium of claim 1 , wherein the operations further comprise outputting, to a display of the client device, a graphical representation of a timer associated with the phrase, wherein the timer displays an amount of time remaining until the phrase expires and a new phrase corresponding to the credential is generated.