.rn '' }`
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..
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.TH BIO_f_cipher 3 "0.9.7d" "2/Sep/2004" "OpenSSL"
.UC
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.rm #[ #] #H #V #F C
.SH "NAME"
BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx \- cipher BIO filter
.SH "SYNOPSIS"
.PP
.Vb 2
\& #include <openssl/bio.h>
\& #include <openssl/evp.h>
.Ve
.Vb 5
\& 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)
.Ve
.SH "DESCRIPTION"
\fIBIO_f_cipher()\fR 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
\fIEVP_CipherInit()\fR, \fIEVP_CipherUpdate()\fR and \fIEVP_CipherFinal()\fR.
.PP
Cipher BIOs do not support \fIBIO_gets()\fR or \fIBIO_puts()\fR. 
.PP
\fIBIO_flush()\fR 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.
.PP
\fIBIO_set_cipher()\fR sets the cipher of BIO \fBb\fR to \fBcipher\fR using key \fBkey\fR
and IV \fBiv\fR. \fBenc\fR should be set to 1 for encryption and zero for
decryption.
.PP
When reading from an encryption BIO the final block is automatically
decrypted and checked when EOF is detected. \fIBIO_get_cipher_status()\fR
is a \fIBIO_ctrl()\fR macro which can be called to determine whether the
decryption operation was successful.
.PP
\fIBIO_get_cipher_ctx()\fR is a \fIBIO_ctrl()\fR 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
\fIBIO_set_cipher()\fR is not flexible enough for the applications needs.
.SH "NOTES"
When encrypting \fIBIO_flush()\fR \fBmust\fR be called to flush the final block
through the BIO. If it is not then the final block will fail a subsequent
decrypt.
.PP
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 read. \fIBIO_get_cipher_status()\fR
should be called to determine if the decrypt was successful.
.PP
As always, if \fIBIO_gets()\fR or \fIBIO_puts()\fR support is needed then it can
be achieved by preceding the cipher BIO with a buffering BIO.
.SH "RETURN VALUES"
\fIBIO_f_cipher()\fR returns the cipher BIO method.
.PP
\fIBIO_set_cipher()\fR does not return a value.
.PP
\fIBIO_get_cipher_status()\fR returns 1 for a successful decrypt and 0
for failure.
.PP
\fIBIO_get_cipher_ctx()\fR currently always returns 1.
.SH "EXAMPLES"
TBA
.SH "SEE ALSO"
TBA

.rn }` ''
.IX Title "BIO_f_cipher 3"
.IX Name "BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx - cipher BIO filter"

.IX Header "NAME"

.IX Header "SYNOPSIS"

.IX Header "DESCRIPTION"

.IX Header "NOTES"

.IX Header "RETURN VALUES"

.IX Header "EXAMPLES"

.IX Header "SEE ALSO"