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+# TREZOR Protocol
+
+## version 1
+
+Messages are sent in packets of 64 bytes.
+
+First packet has the following structure:
+
+| offset | length | type        | contents                                                                              |
+|--------|--------|-------------|---------------------------------------------------------------------------------------|
+|      0 |      3 | char[3]     | '?##' magic constant                                                                  |
+|      3 |      2 | BE uint16_t | numerical [message type](messages.proto#L14)                                          |
+|      5 |      4 | BE uint32_t | message size                                                                          |
+|      9 |     55 | uint8_t[55] | first 55 bytes of message encoded in Protocol Buffers (padded with zeroes if shorter) |
+
+Following packets has the following structure:
+
+| offset | length | type        | contents                                                                               |
+|--------|--------|-------------|----------------------------------------------------------------------------------------|
+|      0 |      1 | char[1]     | '?' magic constant                                                                     |
+|      1 |     63 | uint8_t[63] | following bytes of message encoded in Protocol Buffers (padded with zeroes if shorter) |