Merge !1083

Add blog post about depracation of long payment IDs

See merge request monero-project/monero-site!1083

_posts/2019-06-04-Long-Payment-ID-Deprecation.md

+---
+layout: post
+title: Long Payment ID Deprecation
+summary: Announcement of the deprecation of long payment IDs
+tags: [community, crypto]
+author: dEBRUYNE / Fluffypony
+---
+
+Dear participants of the Monero ecosystem,
+
+We would like to inform you that we will be phasing out long payment
+IDs this year. Long payment IDs are detrimental to privacy and a
+source of negative user experience (as well as additional support work
+for services). Services will have to upgrade to either integrated
+addresses or subaddresses. Note, however, that there is some
+discussion about phasing out integrated addresses as well. Therefore,
+services are, to avoid having to potentially perform additional work,
+encouraged to upgrade to subaddresses directly.
+
+Long payment IDs will be phased out because they have several salient
+drawbacks. First, long payment IDs are detrimental to privacy insofar
+as they can potentially link the transactions of a user in case of
+reusage. Second, long payment IDs have to be attached separately to a
+transaction. This is inconsistent with conventional cryptocurrency
+transactions and therefore unintuitive for the user. As a result,
+users occasionally forget to attach the long payment ID when sending
+their transaction to a service and thus have to go through support to
+'recover' their funds. Third, it logically follows from the previous
+point that long payment IDs cause additional support work for
+services. Fourth, only one long payment ID can be attached to a
+transaction. Thus, services cannot batch withdrawals of multiple users
+specifying a long payment ID. By contrast, subaddresses have no such
+restriction and withdrawals can thus all be batched.
+
+In sum, payment IDs have serveral salient drawbacks and will therefore
+be phased out. Services are recommended to upgrade to subaddresses as
+soon as possible. Subaddresses essentially function similar to Bitcoin
+HD wallets and should thus be relatively straightforward to implement.
+Furthermore, subaddresses are managable from a resource point point of
+view.
+
+Yours sincerely,
+
+The Monero dev community
+
+Appendix:
+
+An upgrade process PDF that may be useful for you can be found here:
+https://github.com/monero-project/meta/files/2775745/Upgrade.Process.pdf