Add binascii encodings to conventions.md

1 files changed, 31 insertions, 0 deletions

diff --git a/spec/intro/conventions.md b/spec/intro/conventions.md
index e474c3a..8a92521 100644
--- a/spec/intro/conventions.md
+++ b/spec/intro/conventions.md
@@ -58,6 +58,37 @@ in big-endian ("network") order.
 > it is the byte 0x00, the byte 0x00, the byte 0x12, and the byte 0x34.
 > (\[00 00 12 34\]).
 
+## Binary-as-text encodings {#binascii}
+
+When we refer to "base64", "base32", or "base16",
+we mean the encodings described in
+[RFC 4648](https://datatracker.ietf.org/doc/html/rfc4648),
+with the following notes:
+
+- In base32, we never insert linefeeds in base32,
+  and we omit trailing `=` padding characters.
+- In base64,
+  we _sometimes_ omit trailing `=` padding characters,
+  and we do not insert linefeeds unless explicitly noted.
+- We do not insert any other whitespace,
+  except as specifically noted.
+
+Base 16 and base 32 are case-insensitive.
+Unless otherwise stated,
+implementations should accept any cases,
+and should produce a single uniform case.
+
+We sometimes refer to base16 as "hex" or "hexadecimal".
+
+> Note that as of 2023, in some places, the specs are not always
+>  explicit about:
+>
+>   - which base64 strings are multiline
+>   - which base32 strings and base16 strings
+>     should be generated in what case.
+>
+> This is something we should correct.
+
 ## Notation {#notation}
 
 ### Operations on byte strings {#ops}