reki2000 / intencoder-go

A UInt64 obfuscation encoder for sequencial ID

intencoder-go

A UInt64 obfuscation encoder for sequencial ID

Motivation

In a simple RDB-based web system, using sequential IDs for entities is not ideal. Such practice allows for the estimation of the business size and increases the risk of ID-guessing attacks.

This library provides a reversible transformation to obfuscate a uint64 into a hard-to-guess string. The resulting string ranges from a minimum of 7 to a maximum of 15 characters (or an array with a minimum of 4 bytes to a maximum of 9 bytes).

• up to 2^24-1 : 7 chars
• up to 2^32-1 : 8
• up to 2^40-1 : 10
• up to 2^48-1 : 12
• up to 2^56-1 : 13
• up to 2^64-1 : 15

To enhance human readability, the encoder utilizes a restricted character set based on base32 encoding. This avoids characters like "0" and "O", "1" and "I", and especially "Q" and "9", as these pairs are easily confused in pronunciation in Japanese ("kyu-").

Example

Code	Decimal Value	Hexadecimal Value
KM4F-DLY	0	0x0
DWE3-QNI	17	0x11
Z3FR-Y4Q	4386	0x1122
GBDK-3DY	1122867	0x112233
WJF3-LN4L	287454020	0x11223344
A6NH-TF27-HI	73588229205	0x1122334455
5EZH-4LSJ-TKRQ	18838586676582	0x112233445566
W43I-TY3I-MLSI-C	4822678189205111	0x11223344556677
VXQB-FS37-LKNN-HAA	1234605616436508552	0x1122334455667788

How to use

TBD

options

• change/remove delimiter character
• keep enough string length for smaller values

Learning

Initially, I attempted to use the Feistel algorithm, but it did not effectively obscure the change in bits across a sequence of original values.

To address this, I added a nonce byte and created a different SHA-256 hash from a salt and nonce. The encryption is performed using a simple XOR operation with the hash.

other notes

• golang hash function performance comparison:

MD5   : 1.074252ms
SHA1  : 1.11365ms
SHA256: 771.172µs
SHA512: 2.29784ms