BIO_f_cipher(3)

     BIO_f_cipher(3)        0.9.6h (2000-09-16)        BIO_f_cipher(3)

     NAME
          BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status,
          BIO_get_cipher_ctx - cipher BIO filter

     SYNOPSIS
           #include <openssl/bio.h>
           #include <openssl/evp.h>

           BIO_METHOD *   BIO_f_cipher(void);
           void BIO_set_cipher(BIO *b,const EVP_CIPHER *cipher,
                          unsigned char *key, unsigned char *iv, int enc);
           int BIO_get_cipher_status(BIO *b)
           int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx)

     DESCRIPTION
          BIO_f_cipher() returns the cipher BIO method. This is a
          filter BIO that encrypts any data written through it, and
          decrypts any data read from it. It is a BIO wrapper for the
          cipher routines EVP_CipherInit(), EVP_CipherUpdate() and
          EVP_CipherFinal().

          Cipher BIOs do not support BIO_gets() or BIO_puts().

          BIO_flush() on an encryption BIO that is being written
          through is used to signal that no more data is to be
          encrypted: this is used to flush and possibly pad the final
          block through the BIO.

          BIO_set_cipher() sets the cipher of BIO <b> to cipher using
          key key and IV iv. enc should be set to 1 for encryption and
          zero for decryption.

          When reading from an encryption BIO the final block is
          automatically decrypted and checked when EOF is detected.
          BIO_get_cipher_status() is a BIO_ctrl() macro which can be
          called to determine whether the decryption operation was
          successful.

          BIO_get_cipher_ctx() is a BIO_ctrl() macro which retrieves
          the internal BIO cipher context. The retrieved context can
          be used in conjunction with the standard cipher routines to
          set it up. This is useful when BIO_set_cipher() is not
          flexible enough for the applications needs.

     NOTES
          When encrypting BIO_flush() must be called to flush the
          final block through the BIO. If it is not then the final
          block will fail a subsequent decrypt.

          When decrypting an error on the final block is signalled by
          a zero return value from the read operation. A successful
          decrypt followed by EOF will also return zero for the final

     Page 1                                         (printed 1/19/103)

     BIO_f_cipher(3)        0.9.6h (2000-09-16)        BIO_f_cipher(3)

          read. BIO_get_cipher_status() should be called to determine
          if the decrypt was successful.

          As always, if BIO_gets() or BIO_puts() support is needed
          then it can be achieved by preceding the cipher BIO with a
          buffering BIO.

     RETURN VALUES
          BIO_f_cipher() returns the cipher BIO method.

          BIO_set_cipher() does not return a value.

          BIO_get_cipher_status() returns 1 for a successful decrypt
          and 0 for failure.

          BIO_get_cipher_ctx() currently always returns 1.

     EXAMPLES
          TBA

     SEE ALSO
          TBA

     Page 2                                         (printed 1/19/103)