Update - We will be testing removal of MD5 Hash value from API responses on 04/23/2019 between 9:00am to 11:00am PT, during this time the MD5 Hash field will be present but the value will be empty.

Additionally the final cut off is being change from Friday June 28, 2019 to Thursday June 27, 2019.
Apr 8, 11:28 PDT

Update - After reviewing feedback concerning the production cutoff date for the MD5 Hash, we are pushing back the production update from March 14, 2019, to June 28, 2019. We will continue to review feedback and consider further date changes as needed over the next month.

For more details, see MD5 Hash End of Life & Signature Key Replacement article - https://support.authorize.net/s/article/MD5-Hash-End-of-Life-Signature-Key-Replacement
Mar 12, 09:29 PDT

Update - The final cut off for MD5 Hash has been changed to March 28th, 2019.

For more details, see our support article, MD5 Hash End of Life & Signature Key Replacement:
https://support.authorize.net/s/article/MD5-Hash-End-of-Life-Signature-Key-Replacement
Mar 1, 08:16 PST

Scheduled - Authorize.Net is phasing out the MD5 based hash use for transaction response verification in favor of the SHA-512 based hash utilizing a Signature Key.

The end of life for MD5 Hash will be done in two phases:

Phase 1 - As of February 11, 2019 we have removed ability to configure or update MD5 Hash setting in the Merchant Interface. Merchants who had this setting configured have already been emailed/contacted.

Phase 2 - Stop sending the MD5 Hash data element in the API response. To continue verifying via hash, this will require applications to support the SHA-512 hash via signature key.

--Sandbox will be updated on March 7, 2019 to stop populating the MD5 Hash value, but the field will still be present but empty.

--Production will be updated on March 14, 2019 to stop populating the MD5 Hash value, but the field will still be present but empty.

For more details, see MD5 Hash End of Life & Signature Key Replacement article - https://support.authorize.net/s/article/MD5-Hash-End-of-Life-Signature-Key-Replacement
Feb 20, 11:17 PST