Logo
One Time Password (HOTP)
Description

Use a 3-digit challenge to generate & verify a corresponding 3-letter response.

Provides higher entropy and security than authentication tables while being easier to use.

Pre-Authenticate:

A->B: AUTH 123 ABC

B->A: ACK. AUTH 456 DEF

Challenge-Response:

A->B: CONFIRM 123

B->A: ACK ABC. CONFIRM 456

A->B: ACK DEF

---
Authentication Tables
Description

Challenge-response tables for authentication.

Example:

A->B: CONFIRM CEY (Table: Charlie, Column: E, Row: Y)

B->A: ACK 7. CONFIRM AIT (Table: Alpha, Column: I, Row: T)

A->B: ACK T

One-Time Pad
Description

Use a 5-digit key to generate a corresponding fixed (paper friendly) or streamed (more secure) cipher.

Cipher values are added to the ASCII encoded message to create encrypted message.

Encoding:
Message: "HI"
Pad Key: 12345
Cipher: 42 85 28 71 14 ...

H = ASCII 72 → 72 + 42 = 114 → Hex 72
I = ASCII 73 → 73 + 85 = 158 → Hex 9E

Encoded: 729E
Decoding:
Encoded: 729E
Pad Key: 12345
Cipher: 42 85 28 71 14 ...

72 (Hex) = 114 → 114 - 42 = 72 → ASCII 'H'
9E (Hex) = 158 → 158 - 85 = 73 → ASCII 'I'

Decoded: "HI"
ASCII Reference Table