| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 281 | SHA-256 Implementation | Hard | CryptographyHashingBit Operations |
| 282 | AES Encryption (Simplified) | Hard | CryptographyEncryptionMatrix |
| 283 | RSA Key Generation | Hard | CryptographyMathPrimes |
| 284 | Diffie-Hellman Key Exchange | Hard | CryptographyMathModular Arithmetic |
| 285 | Merkle Tree Builder | Hard | CryptographyTreeHashing |
| 286 | HMAC Implementation | Hard | CryptographyHashingAuthentication |
| 287 | Password Hasher with Salt | Hard | CryptographyHashingRandom |
| 288 | Digital Signature Simulator | Hard | CryptographyRSAHashing |
| 289 | One-Time Pad Cipher | Hard | CryptographyXORRandom |
| 290 | Zero-Knowledge Proof Demo | Hard | CryptographyMathProtocol |
| 291 | LZ77 Compression | Hard | CompressionStringSliding Window |
| 292 | Run-Length Encoding for Images | Hard | Compression2D ArrayEncoding |
| 293 | Minimax Game AI | Hard | Game TheoryRecursionAlpha-Beta |
| 294 | Monte Carlo Tree Search | Hard | Game TheoryTreeProbability |
| 295 | MapReduce Framework | Hard | Distributed SystemsConcurrencyPartitioning |
| 296 | Raft Consensus Simulator | Hard | Distributed SystemsState MachineProtocol |
| 297 | Build Order with Parallel Execution | Hard | Advanced AlgorithmsGraphTopological Sort |
| 298 | Concurrent Skip List | Hard | ConcurrencySkip ListLock-Free |
| 299 | Custom Allocator with Coalescing | Hard | System DesignMemoryFree List |
| 300 | Database Query Optimizer | Hard | System DesignTreeCost Model |