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AES Encryption/Decryption Tool | CoderTools

Online AES encryption and decryption tool supporting multiple modes like CBC, ECB, for both text and file encryption.

About AES Encryption

AES (Advanced Encryption Standard) is a symmetric encryption algorithm published by NIST in 2001. AES is one of the most widely used encryption algorithms and has been adopted by the US federal government as the encryption standard.

AES supports key lengths of 128, 192, and 256 bits, providing different levels of security. AES-256 is considered the most secure and cannot be cracked in a reasonable time even with the most powerful computers available today.

Encryption Modes

  • CBC: CBC (Cipher Block Chaining): Each plaintext block is XORed with the previous ciphertext block before encryption. Requires IV, more secure, recommended.
  • ECB: ECB (Electronic Codebook): Divides plaintext into fixed-size blocks, each encrypted independently. No IV needed, but less secure, not recommended for sensitive data.
  • CTR: CTR (Counter): Converts block cipher to stream cipher by incrementing a counter to produce keystream. Requires IV, supports parallel encryption, suitable for high-performance scenarios.
  • CFB: CFB (Cipher Feedback): Converts block cipher to stream cipher, using previous ciphertext block as input for next block. Requires IV.
  • OFB: OFB (Output Feedback): Converts block cipher to stream cipher, feeding encryption output back to input. Requires IV.

Encryption Mode Comparison

Mode Security Speed Parallel Processing Error Propagation Recommendation
CBC High Medium Decrypt Only Limited to Adjacent Blocks Most widely used, suitable for general encryption needs
ECB Low Fast Full Support No Propagation Not Recommended - Has security vulnerabilities
CTR High Fast Full Support No Propagation Suitable for high-performance scenarios, supports streaming
CFB High Medium Decrypt Only Limited to Adjacent Blocks Suitable for stream encryption scenarios
OFB High Medium Not Supported No Propagation Suitable for scenarios requiring error tolerance

Security Recommendations

  • 1. Use strong keys: Keys should be randomly generated with a minimum length of 128 bits, 256 bits recommended.
  • 2. Protect keys: Keys are critical for encryption security and must be kept secure, never transmitted over insecure channels.
  • 3. Use secure modes: CBC or CTR modes are recommended, avoid ECB mode.
  • 4. Rotate keys regularly: For long-term systems, encryption keys should be rotated periodically.
  • 5. Use unique IVs: Use a different IV for each encryption, even with the same key.

Key Length Security Comparison

Key Length Bytes Possible Key Combinations Brute Force Time Estimate Performance Usage Recommendation
128-bit 16 bytes 2128 ≈ 3.4×1038 Billions of years (using current technology, assuming 10^18 keys/second) Fastest
Baseline (100%)
 Suitable for most commercial applications, provides sufficient security
192-bit 24 bytes 2192 ≈ 6.3×1057 Far exceeds the age of the universe (theoretically impossible) Medium
~80% of AES-128
 Rarely used, provides higher security than 128-bit
256-bit 32 bytes 2256 ≈ 1.1×1077 Astronomically impossible (even with all energy in the universe) Slower
~60-70% of AES-128 (with AES-NI)
 Suitable for highly sensitive data, government/military applications

Security Note:

AES-128 is already considered secure enough to resist all known attacks. The choice of key length should balance security requirements with performance considerations. For most applications, AES-128 provides sufficient security, while AES-256 is recommended for highly sensitive data. Performance differences are more pronounced with hardware acceleration (AES-NI).

Performance Benchmark (Hardware AES-NI enabled)

Encryption Speed (Modern CPU, typical values)
AES-128
~500 MB/s
AES-192
~425 MB/s
AES-256
~350 MB/s
Decryption Speed (Modern CPU, typical values)
AES-128
~520 MB/s
AES-192
~447 MB/s
AES-256
~369 MB/s

Note: Actual performance varies by hardware, implementation, and data size. Values shown are typical benchmarks on modern CPUs with AES-NI instruction support. Without hardware acceleration, performance may be 10-20x slower.

Use Cases

  • Data transmission encryption: Protect sensitive data during network transmission
  • File encryption: Encrypt sensitive files stored on disk
  • Database encryption: Encrypt sensitive fields in databases
  • Password protection: Encrypt user passwords and authentication information
  • Communication encryption: Encrypt instant messaging and email content

References