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-rw-r--r--packages/meshbay-common/src/meshbay_common/groupbox.py5
1 files changed, 5 insertions, 0 deletions
diff --git a/packages/meshbay-common/src/meshbay_common/groupbox.py b/packages/meshbay-common/src/meshbay_common/groupbox.py
index f1091c3..ff60bba 100644
--- a/packages/meshbay-common/src/meshbay_common/groupbox.py
+++ b/packages/meshbay-common/src/meshbay_common/groupbox.py
@@ -41,6 +41,10 @@ from cryptography.hazmat.primitives.kdf.hkdf import HKDF
PURPOSE_INDEX = "index"
PURPOSE_ACK = "ack"
+# The chat epoch keys themselves, on their way to a member. The keys are what
+# the chat archive is encrypted under; this is only how they travel, which is
+# why rotating the group key costs a re-wrap and not a re-encryption.
+PURPOSE_CHAT_KEYS = "chat_keys"
# `salt=None` here and `salt: new Uint8Array(0)` in crypto.js agree — RFC 5869
# extracts with a zero key either way. Already proven in production by
@@ -48,6 +52,7 @@ PURPOSE_ACK = "ack"
_INFO = {
PURPOSE_INDEX: b"meshbay:index:v1",
PURPOSE_ACK: b"meshbay:ack:v1",
+ PURPOSE_CHAT_KEYS: b"meshbay:chat_keys:v1",
}
NONCE_LEN = 12 # 96-bit, the WebCrypto AES-GCM standard