Introduction
CDMA systems require a
(mostly) unique identifier for mobile devices. This identifier is specific to the
device, and can't (easily) be changed, unlike a phone number (also known as a "MIN").
There are two major identifier types  the older Electronic Serial Number (ESN) and
the newer Mobile Equipment Identifier (MEID). Both identifiers have multiple
presentation formats, and it can be tricky to determine how to actually identify a
device if you're given a number in an unknown format. This document aims to demystify
ESNs and MEIDs.
Electronic Serial Number (ESN)
ESN's are managed by the Telecom Industry
Association. They are 32 bits long (that is, they can be described by a sequence
of 32 1's and 0's), and identify the manufacturer of a mobile device and also
the serial number assigned to the device by that manufacturer.
The basic format for ESN's consists of 8 bits to specify the manufacturer and 24
bits to specify the serial number:
The 8 bits of the manufacturer portion lead to 256 (2^8) different possible
manufacturer codes. Some codes are reserved, however: numbers 0 through
18 , 128 , 250 , and 255 are not to
be used as normal ESNs.
For manufacturer codes 0 through 17 , 250 ,
and 255 , the manufacturer code is 14 bits and the serial number is 18
bits.
Code 128 is discussed below in the pESN section.
It's usually most convenient to assume the standard format, and treat the reserved
codes as exceptions.
The 32 binary bits can be expressed in several ways, but the two recognized ways
are:
 8 character hex code: A 2 character hexadecimal code to represent the
manufacturer, and a 6 character hex code to represent the serial number. This is
the most widely used format. Examples:
0x0106C01B8 (using 0x to
indicate that a hex value follows), 0hC3B80 (using 0h to indicate that
a hex value follows), e5ab0134b (without a prefix).

11 digit decimal code: A 3 digit decimal number to represent the
manufacturer, and an 8 digit decimal number to represent the serial number.
Examples:
23981037459 , 24110201020 . This is the second
most widely used format.
 Beware: some programs (e.g. Microsoft Excel) strip off leading 0's, making
it difficult to tell whether you're looking at a decimal ESN. For example, a
code of
01924100142 might show up as 1924100142 . You
might have as few as 8 digits (a manufacturer code of 000 ), or 9
digits (reserved manufacturer codes 001 through
009 ).
Type 
Manufacturer Code 
Serial Number 
Binary 
8 binary bits 
24 binary bits 
Hexadecimal 
2 hexadecimal numbers 
6 hexadecimal numbers 
Decimal 
3 decimal digits 
8 decimal digits 
To convert between the two, break up your code (in either format) into a
manufacturer block and a serial number block, convert the block to/from decimal/hex
separately, then concatenate the two blocks. Make sure the blocks start and end with
the correct number of hex characters/decimal digits.
 Hex format to decimal format example:
0x0106C01B8 breaks into
0x10 and 0x6C01B8 . 0x10 in decimal is
16 , and 0x6C01B8 is 7078328 . The converted
ESN is 167078328 .
 Decimal format to hex format example:
067078328 breaks into
067 and 078328 . 067 in hex is
0x43 , and 078328 is 0x131F8 . The converted
ESN is 0x43131F8 .
Some improper, but notuncommon ways of representing ESNs are:
 Converting the 11 digit decimal code above straight to hexadecimal (i.e. not
splitting it into 3 digits for the manufacturer and 8 for the serial number). This
can be difficult to detect, as they are also 8 hex digits. If you have a set of 8
character hex codes, check the manufacturer codes. If you consistently see an
uncommon (for you) manufacturer, someone may have given you the ESN in this
improper format. To correct this, convert the hex number back to decimal, then
split up the manufacturer (3 digits) and serial number (8 digits).
 Converting the 8 character hex code above straight to decimal (i.e. not
splitting it into 2 characters for the manufacturer and 6 for the serial number).
This is a little bit easier to detect than the previous improper format, as these
will be a maximum of 10 decimal digits (2^32  1 =4,294,967,295). To correct this,
convert the decimal number back to hex, then split up the manufacturer (2
characters) and the serial number (6 characters).
Resources for ESNs:
Mobile Equipment Identifier (MEID)
MEID's are also manged by the TIA. These are 56
bits long, and like ESN's, identify the manufacturer of a mobile device as
well as the serial number assigned to the device by that manufacturer.
The MEID consists of 32 bits to specify the manufacturer and 24 bits to specify
the serial number: The first 4 bits of the manufacturer code are "reserved," and
restricted to just a few values. There can also be a 4 bit "check digit" appended to
the end, but this is not transmitted between the mobile device and the CDMA system
(according to 3GPP2
S.R0048A) and is not common to see.
There are two proper ways to represent MEIDs:
 14 character hex code: An 8 character hex code to represent the
manufacturer (2 for the reserved portion, 6 for the actual manufacturer portion),
and a 6 character hex code to represent the serial number. This is the most widely
used format. Examples:
0xA10000009296F2 (using 0x to indicate that a
hex value follows), 0hA00000003FF642 (using 0h to indicate that a hex
value follows), ff000000b2c63a (without a prefix).
 18 digit decimal code: A 10 digit decimal number to represent the
manufacturer, and an 8 digit decimal number to represent the serial number.
Example:
268435456010201020 .
Type 
Manufacturer Code 
Serial Number 
Binary 
32 binary bits 
24 binary bits 
Hexadecimal 
8 hexadecimal numbers 
6 hexadecimal numbers 
Decimal 
10 decimal digits 
8 decimal digits 
To convert between the two, break up your code (in either format) into a
manufacturer block and a serial number block, convert the block to/from decimal/hex
separately, then concatenate the two blocks. Make sure the blocks start and end with
the correct number of hex characters/decimal digits.
 Hex format to decimal format example:
0xA10000009296F2 breaks into
0xA1000000 and 0x9296F2 . 0xA1000000 in
decimal is 2701131776 , and 0x9296F2 is
9606898 . The converted manufacturer block is OK (10 decimal digits),
but the serial number block is one short (it's 7 instead of 8), so we prepend a 0
to it. The converted MEID is 270113177609606898 (18 decimal
digits).
 Decimal format to hex format example:
268435456010201020 breaks
into 2684354560 and 10201020 . 2684354560 in
hex is 0xA0000000 , and 10201020 is 0x9BA7BC .
The converted MEID is 0xA00000009BA7BC .
Some improper, but notuncommon ways of representing MEIDs are:
 Converting the 18 digit decimal code above straight to hexadecimal (i.e. not
splitting it into 10 digits for the manufacturer and 8 for the serial number). To
correct this, convert the hex number back to decimal, then split up the
manufacturer (10 digits) and serial number (8 digits).
 Converting the 14 character hex code above straight to decimal (i.e. not
splitting it into 8 characters for the manufacturer and 6 for the serial number).
To correct this, convert the decimal number back to hex, then split up the
manufacturer (8 characters) and the serial number (6 characters).
Tip: For MEIDs, it can be difficult to convert to/from hex/decimal an
improper code, since the numbers are so large (they cause an error if the "integer"
type used in whatever conversion routine is not big enough). If you're using
Excel:
Resources for MEID's:
Pseudo ESN (pESN)
The reserved ESN manufacturer code 128 is for "pseudo ESN's," which allow legacy
equipment to recognize MEIDs. pESN's are ESN codes that always begin with 0x80 in the
hex format (or 128 in the decimal format, but it is much more convenient to work with
the hex format for pESNs). To generate one, you apply the Secure Hash Algorithm 1 (SHA1) to the MEID,
and take the last (least significant) 24 bits (6 hex numbers) of the result, and
append them to 0x80 .
This can be tricky to do, especially if you're using something like Microsoft
Excel. You want to apply SHA1 to the number representing the
MEID, not the string representing the MEID. You'll need to
process it bytebybyte, so you must give it two hex numbers at a time (since two hex numbers make a byte)
and make sure they are interpreted as numbers and not ASCII characters. This VBA script,
which can be used as a userdefined Excel function, does the trick: pESN.txt
Examples:
 Given MEID
0xA0000000002329 , make a pESN. SHA1 on
A0000000002329 gives
e3be267a2cd5c861f3c7ea4224df829a3551f1ab . Take the last 6 hex numbers
of this result, and append it to 0x80  the result is
0x8051F1AB .
 Given MEID
0xFF000001123456 , make a pESN. SHA1 on
"FF000001123456 " gives
ffce4beab4c2a7933c0d6d21b21cf21a0e0737e1 . Take the last 6 hex numbers
of this result, and append it to 0x80  the result is
0x800737E1 .
