added stellar.py to implement get_public_key_from_bytes

trezorlib/stellar.py

@@ -0,0 +1,39 @@
+import base64
+import struct
+
+def get_public_key_from_bytes(pk_bytes):
+    """Returns the base32-encoded version of pk_bytes (G...)
+    """
+    final_bytes = bytearray()
+
+    # version
+    final_bytes.append(6 << 3)
+    # public key
+    final_bytes.extend(pk_bytes)
+    # checksum
+    final_bytes.extend(struct.pack("<H", _crc16_checksum(final_bytes)))
+
+    return base64.b32encode(final_bytes)
+
+def _crc16_checksum(bytes):
+    """Returns the CRC-16 checksum of bytearray bytes
+
+    Ported from Java implementation at: http://introcs.cs.princeton.edu/java/61data/CRC16CCITT.java.html
+
+    Initial value changed to 0x0000 to match Stellar configuration.
+    """
+    crc = 0x0000
+    polynomial = 0x1021
+
+    count = 0
+    for byte in bytes:
+        count = count + 1
+
+        for i in range(0, 8):
+            bit = ((byte >> (7 - i) & 1) == 1)
+            c15 = ((crc >> 15 & 1) == 1)
+            crc <<= 1
+            if c15 ^ bit:
+                crc ^= polynomial
+
+    return crc & 0xffff