It is easy for the base station to ensure that all PLCM codes are unique when this is done. This specification also allows the PLCM to be based on the MEID or IMSI. A different problem occurs when ESN codes are stored in a database (such as for OTASP). In this situation, the risk of at least two phones having the same pseudo-ESN can be calculated using the birthday paradox and works out to about a 50 per cent probability in a database with 4,800 pseudo-ESN entries. 3GPP2 specifications C.S0016 (Revision C or higher) and C.S0066 have been modified to allow the replacement MEID identifier to be transmitted, resolving this problem. Another problem is that messages delivered on the forward paging channel using the pESN as an address could be delivered to multiple mobiles seemingly randomly. This problem can be avoided by using mobile identification number (MIN) or IMSI based addressing instead. This short Python script will convert an MEID to a pESN.  import hashlib  meid = input("Enter a MEID: ").upper()  bytes = bytearray.fromhex(meid) s = hashlib.sha1(bytes)  pesn = "80" + s.hexdigest()[-6:].upper()  print("pESN: " + pesn) The CDG also provides a javascript calculator with more conversion options. This C# method will convert an MEID from HEX to DEC format (or return empty for an invalid MEID HEX value)  public static string HexToDecimal(string input)