XChaCha20-Poly1305
Extended ChaCha20-Poly1305 authenticated encryption with 192-bit nonces. Provides the security and performance of ChaCha20-Poly1305 while eliminating nonce size limitations.
Properties
| Property |
Value |
| Category |
Special Algorithms |
| Sub-category |
AEAD Cipher |
| Security status |
🎓 Educational Only |
| Complexity |
Intermediate |
| Inventor |
Scott Arciszewski (libsodium team) |
| Year |
2018 |
| Origin |
🇺🇸 United States |
| Source |
algorithms/special/xchacha20-poly1305.js |
Parameters
| Parameter |
Supported values |
| Key sizes |
32 bytes (256 bits) |
| Tag sizes |
16 bytes (128 bits) |
Capabilities
| Flag |
Value |
SupportsDetached |
No |
Security
Status: 🎓 Educational Only
Known vulnerabilities
| Issue |
Description |
Mitigation |
| Key Reuse |
Extended nonces reduce but don’t eliminate nonce reuse risks |
Still ensure nonces are not reused, though collision probability is negligible |
Documentation
References
Test vectors
2 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.
Vector 1 — XChaCha20-Poly1305 RFC draft-irtf-cfrg-xchacha-03 Appendix A
| Field |
Value |
key |
808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f |
nonce |
404142434445464748494a4b4c4d4e4f5051525354555657 |
aad |
50515253c0c1c2c3c4c5c6c7 |
input |
4c616469657320616e642047656e746c 656d656e206f662074686520636c6173 73206f66202739393a20496620492063 6f756c64206f6666657220796f75206f 6e6c79206f6e652074697020666f7220 746865206675747572652c2073756e73 637265656e20776f756c642062652069 742e |
expected |
bd6d179d3e83d43b9576579493c0e939 572a1700252bfaccbed2902c21396cbb 731c7f1b0b4aa6440bf3a82f4eda7e39 ae64c6708c54c216cb96b72e1213b452 2f8c9ba40db5d945b11b69b982c1bb9e 3f3fac2bc369488f76b2383565d3fff9 21f9664c97637da9768812f615c68b13 b52ec0875924c1c7987947deafd8780a cf49 |
Vector 2 — XChaCha20-Poly1305 Empty Input Test (Corrected)
| Field |
Value |
key |
0000000000000000000000000000000000000000000000000000000000000000 |
nonce |
000000000000000000000000000000000000000000000000 |
aad |
(empty) |
input |
(empty) |
expected |
8f3b945a51906dc8600de9f8962d00e6 |
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