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ANSI X9.23

ANSI X9.23 padding scheme fills blocks with zero bytes except for the last byte, which indicates the padding length. This scheme is commonly used in financial cryptographic applications and provides a deterministic padding method suitable for block ciphers.

Properties

Property	Value
Category	Padding Schemes
Sub-category	Block Padding
Security status	🛡️ Secure
Complexity	Not specified
Inventor	ANSI
Year	1998
Origin	🇺🇸 United States
Source	algorithms/padding/ansi-x923.js

Capabilities

Flag	Value
IsLengthIncluded	No

Security

Status: 🛡️ Secure

Known vulnerabilities

Issue	Description	Mitigation
Padding Oracle	Like other padding schemes, ANSI X9.23 can be vulnerable to padding oracle attacks if error messages reveal padding validity.	—
Length Disclosure	The padding scheme reveals information about the original message length modulo block size.	—

Documentation

• ANSI X9.23 Standard
• Financial Cryptographic Standards
• Padding in Cryptography

References

• ANSI X9 Committee
• Financial Services Cryptography
• Block Cipher Padding

Test vectors

3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — ANSI X9.23 padding with 17 bytes needed

Source: ANSI X9.23 Standard

Field	Value
blockSize	32
input	6bc1bee22e409f96e93d7e11739317
expected	6bc1bee22e409f96e93d7e117393170000000000000000000000000000000011

Vector 2 — ANSI X9.23 padding with 18 bytes needed

Source: ANSI X9.23 Standard

Field	Value
blockSize	32
input	6bc1bee22e409f96e93d7e117393
expected	6bc1bee22e409f96e93d7e117393000000000000000000000000000000000012

Vector 3 — ANSI X9.23 padding with 59 bytes needed

Source: ANSI X9.23 Standard

Field	Value
blockSize	64
input	6bc1bee22e
expected	6bc1bee22e0000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 0000000000000000000000000000003b

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