Added warning regarding Lack of Round-trip Compatibility between BIP-39 and SLIP-39.

Author: wolfmcnally

README.md

@@ -63,6 +63,18 @@ These are other projects that work with or leverage *LetheKit*.
 
 - (submit a PR to this repo list your project)
 
+### Known Issues
+
+#### ⚠️ Warning: Lack of Round-trip Compatibility between BIP-39 and SLIP-39
+
+At first glance, BIP-39 and SLIP-39 both appear to be means of converting a binary seed to a set of backup words and back. You might assume you could simply convert a BIP-39 backup to a binary seed, from that binary seed to SLIP-39, and then use the SLIP-39 backup to recover the same wallet as the original BIP-39 backup, but this is **NOT** the case. This is because the SLIP-39 algorithm that SatoshiLabs uses in their Trezor wallet does not derive the master secret in the same way as their BIP-39 algorithm does.
+
+Currently Blockchain Commons is investigating an alternative to SLIP-39 that allows round-trips with BIP-39. We want to ensure that the same seed will result in the same derived keys using either BIP-39 or our alternative approach.
+
+As SLIP-39 is not round-trip compatible with BIP-39, and SLIP-39 is under the control of SatoshiLabs and does not appear to be a fully community-controlled standard, Blockchain Commons is no longer endorsing SLIP-39.
+
+* This issue is being tracked [here](https://github.com/BlockchainCommons/bc-lethekit/issues/38).
+
 ## Financial Support
 
 *LetheKit* (lee-thee kit) is a project of [Blockchain Commons](https://www.blockchaincommons.com/). We are proudly a "not-for-profit" social benefit corporation committed to open source & open development. Our work is funded entirely by donations and collaborative partnerships with people like you. Every contribution will be spent on building open tools, technologies, and techniques that sustain and advance blockchain and internet security infrastructure and promote an open web.