Rationale for duplicating the pkey context in EVP_DigestVerifyFinal

[Christian Schmidt <schmidt@xxxxxxxxx>]

Hi,

In EVP_DigestVerifyFinal() in crypto/evp/m_sigver.c this code exists:

[...]
    dctx = EVP_PKEY_CTX_dup(pctx);
    if (dctx == NULL)
        return 0;

    r = dctx->op.sig.signature->digest_verify_final(dctx->op.sig.algctx,
                                                    sig, siglen);
    EVP_PKEY_CTX_free(dctx);
[...]

I wonder why this is is duplicated before the final so I can handle the 
duplication according to the intention for an Ed25519 Init-Update-Final 
implementation?

Best regards,
Chris