* std.crypto: add AES-CCM and CBC-MAC
Add AES-CCM (Counter with CBC-MAC) authenticated encryption and
CBC-MAC message authentication code implementations to the standard
library.
AES-CCM combines CTR mode encryption with CBC-MAC authentication as
specified in NIST SP 800-38C and RFC 3610. It provides authenticated
encryption with support for additional authenticated data (AAD).
CBC-MAC is a simple MAC construction used internally by CCM, specified
in FIPS 113 and ISO/IEC 9797-1.
Includes comprehensive test vectors from RFC 3610 and NIST SP 800-38C.
* std.crypto: add CCM* (encryption-only) support to AES-CCM
Implements CCM* mode per IEEE 802.15.4 specification, extending
AES-CCM to support encryption-only mode when tag_len=0. This is
required by protocols like ZigBee, Thread, and WirelessHART.
Changes:
- Allow tag_len=0 for encryption-only mode (no authentication)
- Skip CBC-MAC computation when tag_len=0 in encrypt/decrypt
- Correctly encode M'=0 in B0 block for CCM* mode
- Add Aes128Ccm0 and Aes256Ccm0 convenience instances
- Add IEEE 802.15.4 test vectors and CCM* tests
* std.crypto: add doc comments for AES-CCM variants
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