harmony 鸿蒙Key Agreement Overview and Algorithm Specifications

2025-06-12
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Key Agreement Overview and Algorithm Specifications

Key agreement allows two or more parties to jointly establish a shared key in a non-secure environment.

This topic describes the key agreement algorithms and specifications supported by the system.

ECDH

The Crypto framework provides a variety of Elliptic Curve Diffie–Hellman key exchange (ECDH) capabilities.

When creating an ECDH key agreement instance, you need to specify the algorithm specifications in a string parameter, as listed in the table below.

Asymmetric Key Algorithm	String Parameter	API Version
ECC	ECC224	9+
ECC	ECC256	9+
ECC	ECC384	9+
ECC	ECC521	9+
ECC	ECC_BrainPoolP160r1	11+
ECC	ECC_BrainPoolP160t1	11+
ECC	ECC_BrainPoolP192r1	11+
ECC	ECC_BrainPoolP192t1	11+
ECC	ECC_BrainPoolP224r1	11+
ECC	ECC_BrainPoolP224t1	11+
ECC	ECC_BrainPoolP256r1	11+
ECC	ECC_BrainPoolP256t1	11+
ECC	ECC_BrainPoolP320r1	11+
ECC	ECC_BrainPoolP320t1	11+
ECC	ECC_BrainPoolP384r1	11+
ECC	ECC_BrainPoolP384t1	11+
ECC	ECC_BrainPoolP512r1	11+
ECC	ECC_BrainPoolP512t1	11+
ECC	ECC_Secp256k1	14+
ECC	ECC	10+

As indicated by the last row in the preceding table, you can specify the ECDH key type without the key length and curve name to ensure compatibility with the key generated based on the key parameter. In this case, the key agreement operation varies depending on the actual key length.

X25519

The Crypto framework provides X25519 key agreement capabilities.

When creating an X25519 key agreement instance, you need to specify the algorithm specifications in a string parameter, as listed in the table below.

Asymmetric Key Algorithm	String Parameter	API Version
X25519	X25519	11+

DH

The Crypto framework provides Diffie–Hellman key exchange (DH) key agreement capabilities.

When creating a DH key agreement instance, you need to specify the algorithm specifications in a string parameter, as listed in the table below.

Asymmetric Key Algorithm	String Parameter	API Version
DH	DH_modp1536	11+
DH	DH_modp2048	11+
DH	DH_modp3072	11+
DH	DH_modp4096	11+
DH	DH_modp6144	11+
DH	DH_modp8192	11+
DH	DH_ffdhe2048	11+
DH	DH_ffdhe3072	11+
DH	DH_ffdhe4096	11+
DH	DH_ffdhe6144	11+
DH	DH_ffdhe8192	11+
DH	DH	11+

As indicated by the last row in the preceding table, you can specify the DH key type without the named DH group to ensure compatibility with the key generated based on the key parameter. In this case, the key agreement result is determined by the key passed in. In addition, unnamed DH groups are supported.