Mathematical Pipeline Formulations

This technical reference defines the exact mathematical formulations, cryptographic stretching, pseudorandom spatial mapping, and bitwise transformations driving the STEGNOLINES engine.

1. Dynamic Key & Counter Derivation (PBKDF2-HMAC-SHA256)

To eliminate pre-shared salts while preventing replay attacks, a deterministic 16-byte cryptographic salt $S$ is extracted directly from the cover text:

The cryptographic key material is generated by executing 100,000 iterations of PBKDF2:

2. Symmetric Cipher Stream (AES-256-CTR)

AES in Counter Mode (CTR) functions as a stream cipher, providing high execution performance with exactly zero padding overhead:

3. Cryptographic CSPRNG Seeding & Spatial Placement

The Stego-Key string is derived into a 256-bit cryptographic seed using PBKDF2-HMAC-SHA256 across 100,000 iterations with a domain-specific salt:

An AES-256-CTR CSPRNG combined with Unbiased Rejection Sampling eliminates modulo bias completely and generates deterministic, uniform random indices $P = [p_1, p_2, ..., p_K]$ in the cover text via an $O(K)$ Lazy Fisher-Yates shuffle. (A legacy fallback engine using DJB2 + Mulberry32 is maintained for backward compatibility with previous version messages).

4. Bitwise XOR Masking & Recovery

For each message bit $m_j$ and selected cover bit $c_{p_j}$, the XOR key bit $k_j$ is computed as:

During extraction, the exact message bit is recovered using the same cover bits:

Since $(c_{p_j} \oplus m_j) \oplus c_{p_j} = m_j$, perfect bit-for-bit lossless data reconstruction is mathematically guaranteed.

5. Variation Selector Mapping