Contents

GFpECKeyExchangeSM2_SharedKey

Computes a shared key between two participants of the cryptosystem.

Syntax

IppStatus ippsGFpECKeyExchangeSM2_SharedKey(Ipp8u* pSharedKey, int sharedKeySize, Ipp8u* pSSelf, const IppsBigNumState* pPrvKey, IppsBigNumState* pEphPrvKey, IppsGFpECKeyExchangeSM2State pKE, Ipp8u pScratchBuffer)

Include Files

ippcp.h

Parameters

pSharedKey

Pointer to the secret-number Shared Key.

sharedKeySize

length to the secret-number Shared Key.

pSSelf

Pointer (NULL - optional) to the Self Conformation hash data.

pPrvKey

Pointer to the private keys of the elliptic curve.

pEphPrvKey

Ephemeral Pointer to the private keys of the elliptic curve. Is cleared inside of the function if returned status is ippStsNoErr.

pScratchBuffer

Pointer to the scratch buffer for the elliptic curve.

pKE

Pointer to the buffer begging initialization.

Description

The function computes a secret-number pSharedKey, which is a secret key shared between two participants of the cryptosystem.

Note

The ephemeral public(R_a/b) and private(r_a/b) keys (steps A1-A3 and B1-B3) have to be generated by the user’s application.

[GBT.32918.3-2016] Public Key cryptographic algorithm SM2 based on elliptic curves.

Part 3: Key exchange protocol

6.2 Process of key exchange protocol

stack compute[standart link]:

[user A| user B]

  1. x(a/b)` = 2^w + (x(a/b) & (2^w – 1))

[step 4| step 3]

  1. t(a/b) = (d(a/b) + x(a/b)`*r(a/b) ) mod n

[step 5| step 4]

  1. x(b/a)` = 2^w + ( x(b/a) & (2^w – 1) )

[step 6| step 5]

5) U/V = [h*t(a/b)]( P(b/a) + [x(b/a)`]R(b/a) ) = ( x(u/v), y(u/v) ) tmp_p = SM3( x(u/v) || Za || Zb || xa || ya || xb || yb )

[step 7| step 6]

  1. S(a/b) = SM3( 0x0(3/2) || y(u/v) || tmp_p )

[step 10| step 8]

  1. K(a/b) = KDF(x(u/v) || y(u/v) || Za || Zb, klen)

[step 8| step 7]

Shared secret shared is an SM3 hash digest of the secret point on the elliptic curve.

Return Values

ippStsNoErr

Indicates no error. Any other value indicates an error or warning.

ippStsNullPtrErr

Indicates an error condition if any of the specified pointers are NULL.

ippStsContextMatchErr

Indicates an error condition if the IppsGFpECState context parameter does not match the operation or public keys are set up incorrectly.

ippStsNotSupportedModeErr

Indicates an error condition if the IppsGFpECState context parameter defines an elliptic curve over an extension of the prime finite field.

ippStsRangeErr

Indicates an error condition if the length in bits of the elliptic curve is less than the length in bits of the SM3 hash digest.

ippStsBadArgErr

Indicates an error condition if the role is not equal to ippKESM2Requester or ippKESM2Responder.

ippStsInvalidPrivateKey

Indicates an error condition if the secret key is not within (0, order).

ippStsOutOfRangeErr

Indicates an error condition if sharedKeySize <= 0.

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GFpECKeyExchangeSM2_Setup

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GFpECKeyExchangeSM2_Confirm