first commit, SM2-DSA only

doc/crypto/EVP_OpenInit.pod

@@ -0,0 +1,63 @@
+=pod
+
+=head1 NAME
+
+EVP_OpenInit, EVP_OpenUpdate, EVP_OpenFinal - EVP envelope decryption
+
+=head1 SYNOPSIS
+
+ #include <openssl/evp.h>
+
+ int EVP_OpenInit(EVP_CIPHER_CTX *ctx,EVP_CIPHER *type,unsigned char *ek,
+		int ekl,unsigned char *iv,EVP_PKEY *priv);
+ int EVP_OpenUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
+         int *outl, unsigned char *in, int inl);
+ int EVP_OpenFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
+         int *outl);
+
+=head1 DESCRIPTION
+
+The EVP envelope routines are a high level interface to envelope
+decryption. They decrypt a public key encrypted symmetric key and
+then decrypt data using it.
+
+EVP_OpenInit() initializes a cipher context B<ctx> for decryption
+with cipher B<type>. It decrypts the encrypted symmetric key of length
+B<ekl> bytes passed in the B<ek> parameter using the private key B<priv>.
+The IV is supplied in the B<iv> parameter.
+
+EVP_OpenUpdate() and EVP_OpenFinal() have exactly the same properties
+as the EVP_DecryptUpdate() and EVP_DecryptFinal() routines, as 
+documented on the L<EVP_EncryptInit(3)|EVP_EncryptInit(3)> manual
+page.
+
+=head1 NOTES
+
+It is possible to call EVP_OpenInit() twice in the same way as
+EVP_DecryptInit(). The first call should have B<priv> set to NULL
+and (after setting any cipher parameters) it should be called again
+with B<type> set to NULL.
+
+If the cipher passed in the B<type> parameter is a variable length
+cipher then the key length will be set to the value of the recovered
+key length. If the cipher is a fixed length cipher then the recovered
+key length must match the fixed cipher length.
+
+=head1 RETURN VALUES
+
+EVP_OpenInit() returns 0 on error or a non zero integer (actually the
+recovered secret key size) if successful.
+
+EVP_OpenUpdate() returns 1 for success or 0 for failure.
+
+EVP_OpenFinal() returns 0 if the decrypt failed or 1 for success.
+
+=head1 SEE ALSO
+
+L<evp(3)|evp(3)>, L<rand(3)|rand(3)>,
+L<EVP_EncryptInit(3)|EVP_EncryptInit(3)>,
+L<EVP_SealInit(3)|EVP_SealInit(3)>
+
+=head1 HISTORY
+
+=cut