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SBE Issues Guidance About RWT Failure

Required Weekly Test from IPAWS came with wrong signature

The Society of Broadcast Engineers has issued helpful guidance to stations about what to do in light of the failure of an IPAWS Required Weekly Test on Monday.

“When FEMA issues an IPAWS test or alert it includes a ‘certificate,’” SBE explained in an email to members.

“This operates similar to a password for accessing different sites or files on a computer. In the case of a message from FEMA, a message without a correct signature, the EAS device should ignore the message.”

SBE reported that on Monday, April 26, the Required Weekly Test from IPAWS was transmitted with an incorrect signature.

“The test messages had a mismatch between the digest inside the message, and the digest computed by receivers. This is a part of the validation for an alert, and checking it is required by FCC Rule 11.56(c): ‘EAS Participants shall configure their systems to reject all CAP-formatted EAS messages that include an invalid digital signature.’”

[Read: FCC Will Explore EAS on the Internet]

SBE emphasized that all EAS devices should have rejected the test including units made by Sage Alerting Systems, Digital Alert Systems and Trilithic. The advisory describes how various models should have responded and what you should do next; read that here.

It also said all EAS units would have reported failed validations in a temporary log, and that users should check with their device manufacturer for the location of that file and the correct “signature validation” settings for the unit.

“Stations should check and correct any issues before the next test on May 3, 2021. Stations should insert a note in the station log indicating the failed test and the reason for failure.”