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 * RFC_0011: [Duniter_Blockchain_Protocol_V13](https://git.duniter.org/documents/rfcs/blob/dubp_v13/rfc/0011_Duniter_Blockchain_Protocol_V13.md)
 * RFC_0012: [Duniter Key File Format](https://git.duniter.org/documents/rfcs/blob/authentication_file_format/rfc/0012_duniterkey_authentication_file_format_v1.md)
 * RFC_0015: [HD wallet](https://git.duniter.org/documents/rfcs/blob/hd_wallet/rfc/0015_Dubp_HD_Wallet.md)
+* RFC_0018: [Multilang Mnemonic](https://git.duniter.org/tuxmain/rfcs/-/blob/rfc18_multilang_mnemonic/rfc/0018_Multilang_Mnemonic.md)
 
 ### Discontinued RFCs
 
diff --git a/rfc/0018_Multilang_Mnemonic.md b/rfc/0018_Multilang_Mnemonic.md
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+# #18 Multilang Mnemonic
+
+```txt
+RFC: 18
+Title: Multilang Mnemonic
+Type: Convention
+Status: WIP
+Author: tuxmain <tuxmain@zettascript.org>
+Created: 2024-10-16
+Last edited: 2024-10-16
+License: AGPL-3
+```
+
+This RFC defines how to use multilang mnemonics in an alternative way than defined by [BIP39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki) while staying compatible with it.
+
+## Motivation
+
+Vanilla BIP39 discourages using non-English mnemonics and only few libraries and applications handle them. Users who want a non-English mnemonic thus loose compatibility with most of the ecosystem.
+
+## English mnemonics
+
+Mnemonics in English follow BIP39.
+
+## Non-English mnemonics
+
+BIP39 defines multilang (non-English) mnemonics using the hash of the sentence in the mnemonic's language.
+
+A dictionary `D` of size `N` is an ordered list that contains the distinct words `D(1), ..., D(N)`.
+
+All dictionaries have the same size `N`.
+
+Let `E` be the English dictionary, and `M` a multilang dictionary.
+
+The only change of the present RFC with respect to BIP39 is that in the hash's input, each word `M(i)` is replaced with the corresponding English word `E(i)`.
+
+Applications SHOULD allow the user to export their multilang mnemonic to English (using the inverse bijection) to allow full compatibility with BIP39.
+
+## Example
+
+| index | English Dictionary | French Dictionary |
+| ----- | ------------------ | ----------------- |
+|     0 | energy             | dotation          |
+|     1 | curve              | commande          |
+|     0 | energy             | dotation          |
+|     2 | pepper             | naufrage          |
+|     3 | sort               | révulsif          |
+|     4 | weasel             | ventouse          |
+|     5 | yellow             | voyelle           |
+
+The French mnemonic `dotation ventouse naufrage` generates the same seed as the English mnemonic `energy weasel pepper`.