The Encrypting PIN Pad (EPP4) has two visual indicators, a green LED and a red LED, located on the power CCA. The LEDs provide a method of determining the status of the EPP4 during operation. Table 2-1 contains a description of the LED stages of operation and specific failure modes.
2.1 Normal OperationThe Encrypting PIN Pad (EPP4) provides 2 on-board LEDs on the power CCA. The LEDs provide a visual indication of the present operational stage of the EPP4. Table 2-1 lists the normal operation of the Encrypting PIN Pad (EPP4) in order of occurrence after power-up.
Table 2-1 LED Indicator Stages During Normal Operation
Red Green Indication Comment
OnOnPerforming hash checkChecking the code integrity by performing hash check on entire EPP4 code. Hash checking takes approximately 10 secondsOffOnApplication performing cold startTakes very short time (Hardly noticeable)OffBlinking 2 HzCold start concludedThe application is waiting for the first command and the initial certificates are loadedOffOffThe EPP4 has executed its first commandPower must be OnBlinking 2HzOffExternal communication: The application is waiting for the first command and the initial certificates are not loadedIf certificates are required, the EPP will need to be replacedOn while command is in processOffThe LED is turned on when a command has begun executing and is turned off when a response is returnedThe length of time that the red led remains on is variable, and depends upon the time required for the EPP4 to execute the commandOnOffSecure PIN and DEA (data encryption algorithm) key entryLED remains on until required PIN digits or DEA key are entered.Rapid flashingOnDuring exchange of various download commandsDownload takes approximately two to three minutes.
2.2 FailuresIf the EPP4 fails to complete the normal operation stages listed in Table 2-1, then a possible failure has occurred. Use Table 2-2 to identify failure conditions.
Table 2-2 EPP4 Failure Conditions
Red Green Indication Comment
OnOnThe EPP4 contains no valid bootstrap loader nor a valid applicationIf both LEDs are on longer than 60 seconds, then the EPP4 needs repair. The firmware cannot load. Send the unit for repair.OffOnThe EPP4 contains a valid bootstrap loader Re-boot the terminal processor once or twice to automatically recover from this failure mode. If the error persists, replace the unit.Blinking 2 HzOffExternal communication: The application is waiting for the first command and the initial certificates are not loadedIf this is observed and certificates are required, send the unit for certificate loading.Blinking 6 HzOffKuhn attack prevention activatedCommunication will be possible again after 30 minutes of uninterrupted power (Refer to Kuhn Attack Section 2.2.1).
A Kuhn attack is a method used by hackers to retrieve sensitive information by rapidly and repeatedly power failing a device.
22.214.171.124 Kuhn Attack Mode
Certification standards require that the EPP4 protect itself against Kuhn attacks. To prevent such an attack, the EPP4 invokes a Kuhn attack mode when the total number of rapid, repeated power-up and power-down cycles reaches 64.
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