SecureBit.chat - P2P Encrypted Messenger Files

Fixes file transfers that silently failed to reach the peer, and relaxes the overly strict file-type check that rejected legitimate files.

Fixed

• File chunks are now sized so the on-the-wire message stays under the 64 KB SCTP message-size limit enforced by WebRTC. Previously each 64 KB chunk became a ~87 KB encrypted+Base64 message that exceeded this limit, so the consent handshake succeeded but no data was ever delivered — most visibly on Safari and cross-browser connections whose SDP omits a=max-message-size. The send chunk size is now 16 KB (~22 KB on the wire); inbound chunks up to 64 KB are still accepted for backward compatibility.

Changed

• File-type validation is now driven by the extension allow-list, with the (client-supplied, easily spoofed) MIME type treated as an advisory signal. Files with a missing MIME type or a cross-OS MIME variant (e.g. application/x-zip-compressed for .zip, image/jpg for .jpg) are no longer rejected. Blocked executable/script extensions, a blatantly foreign MIME on a safe extension, and per-type size limits are still enforced.