Authorize.Net has decided to retire their MD5 signature solution in favor of a new and more secure SHA512 based alternative.
--------------------------------------- Timeline ----------------------------------------------------------
Their timeline as far as we have been informed is as follows:
Phase 1 - Remove ability to configured/update MD5 Hash setting in the Merchant Interface by end of January 2019/early February 2019. This change has no impact to the API response; it will be done in Phase 2.
Phase 2 - Stop sending the MD5 Hash data element in the API response. The date for this change will be announced at a later time but is expected in the next 2-3 months.
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We are currently talking to the technical staff at Authorize.Net to figure out how this will affect iPayment, but based on our own investigation, this change should not affect our integration.