.rn '' }`
'''
'''
.de Sh
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp
.if t .sp .5v
.if n .sp
..
.de Ip
.br
.ie \\n(.$>=3 .ne \\$3
.el .ne 3
.IP "\\$1" \\$2
..
.de Vb
.ft CW
.nf
.ne \\$1
..
.de Ve
.ft R

.fi
..
'''
'''
'''     Set up \*(-- to give an unbreakable dash;
'''     string Tr holds user defined translation string.
'''     Bell System Logo is used as a dummy character.
'''
.tr \(*W-|\(bv\*(Tr
.ie n \{\
.ds -- \(*W-
.ds PI pi
.if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
.ds L" ""
.ds R" ""
'''   \*(M", \*(S", \*(N" and \*(T" are the equivalent of
'''   \*(L" and \*(R", except that they are used on ".xx" lines,
'''   such as .IP and .SH, which do another additional levels of
'''   double-quote interpretation
.ds M" """
.ds S" """
.ds N" """""
.ds T" """""
.ds L' '
.ds R' '
.ds M' '
.ds S' '
.ds N' '
.ds T' '
'br\}
.el\{\
.ds -- \(em\|
.tr \*(Tr
.ds L" ``
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.ds PI \(*p
'br\}
.\"	If the F register is turned on, we'll generate
.\"	index entries out stderr for the following things:
.\"		TH	Title 
.\"		SH	Header
.\"		Sh	Subsection 
.\"		Ip	Item
.\"		X<>	Xref  (embedded
.\"	Of course, you have to process the output yourself
.\"	in some meaninful fashion.
.if \nF \{
.de IX
.tm Index:\\$1\t\\n%\t"\\$2"
..
.nr % 0
.rr F
.\}
.TH EVP_SealInit 3 "0.9.5a" "22/Jul/2000" "OpenSSL"
.UC
.if n .hy 0
.if n .na
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.de CQ          \" put $1 in typewriter font
.ft CW
'if n "\c
'if t \\&\\$1\c
'if n \\&\\$1\c
'if n \&"
\\&\\$2 \\$3 \\$4 \\$5 \\$6 \\$7
'.ft R
..
.\" @(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2
.	\" AM - accent mark definitions
.bd B 3
.	\" fudge factors for nroff and troff
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.	ds #H 0
.	ds #V .8m
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.	ds #[ \f1
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.\}
.if t \{\
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.	\" simple accents for nroff and troff
.if n \{\
.	ds ' \&
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.	ds ? \s-2c\h'-\w'c'u*7/10'\u\h'\*(#H'\zi\d\s+2\h'\w'c'u*8/10'
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.	ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.	ds q o\h'-\w'o'u*8/10'\s-4\v'.4m'\z\(*i\v'-.4m'\s+4\h'\w'o'u*8/10'
.\}
.	\" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
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.ds v \\k:\h'-(\\n(.wu*9/10-\*(#H)'\v'-\*(#V'\*(#[\s-4v\s0\v'\*(#V'\h'|\\n:u'\*(#]
.ds _ \\k:\h'-(\\n(.wu*9/10-\*(#H+(\*(#F*2/3))'\v'-.4m'\z\(hy\v'.4m'\h'|\\n:u'
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.ds 3 \*(#[\v'.2m'\s-2\&3\s0\v'-.2m'\*(#]
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
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.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.ds oe o\h'-(\w'o'u*4/10)'e
.ds Oe O\h'-(\w'O'u*4/10)'E
.	\" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.	\" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.	ds : e
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.	ds . \h'-1'.
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.	ds D- D\h'-1'\(hy
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.	ds ae ae
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.\}
.rm #[ #] #H #V #F C
.SH "NAME"
EVP_SealInit, EVP_SealUpdate, EVP_SealFinal \- EVP envelope encryption
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.PP
.Vb 1
\& #include <openssl/evp.h>
.Ve
.Vb 6
\& int EVP_SealInit(EVP_CIPHER_CTX *ctx, EVP_CIPHER *type, unsigned char **ek,
\&                int *ekl, unsigned char *iv,EVP_PKEY **pubk, int npubk);
\& void EVP_SealUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
\&         int *outl, unsigned char *in, int inl);
\& void EVP_SealFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
\&         int *outl);
.Ve
.SH "DESCRIPTION"
The EVP envelope routines are a high level interface to envelope
encryption. They generate a random key and then \*(L"envelope\*(R" it by
using public key encryption. Data can then be encrypted using this
key.
.PP
\fIEVP_SealInit()\fR initialises a cipher context \fBctx\fR for encryption
with cipher \fBtype\fR using a random secret key and IV supplied in
the \fBiv\fR parameter. \fBtype\fR is normally supplied by a function such
as \fIEVP_des_cbc()\fR. The secret key is encrypted using one or more public
keys, this allows the same encrypted data to be decrypted using any
of the corresponding private keys. \fBek\fR is an array of buffers where
the public key encrypted secret key will be written, each buffer must
contain enough room for the corresponding encrypted key: that is
\fBek[i]\fR must have room for \fBEVP_PKEY_size(pubk[i])\fR bytes. The actual
size of each encrypted secret key is written to the array \fBekl\fR. \fBpubk\fR is
an array of \fBnpubk\fR public keys.
.PP
\fIEVP_SealUpdate()\fR and \fIEVP_SealFinal()\fR have exactly the same properties
as the \fIEVP_EncryptUpdate()\fR and \fIEVP_EncryptFinal()\fR routines, as 
documented on the the \fIEVP_EncryptInit(3)|EVP_EncryptInit(3)\fR manpage manual
page. 
.SH "RETURN VALUES"
\fIEVP_SealInit()\fR returns \-1 on error or \fBnpubk\fR if successful.
.PP
\fIEVP_SealUpdate()\fR and \fIEVP_SealFinal()\fR do not return values.
.SH "NOTES"
Because a random secret key is generated the random number generator
must be seeded before calling \fIEVP_SealInit()\fR.
.PP
The public key must be RSA because it is the only OpenSSL public key
algorithm that supports key transport.
.PP
Envelope encryption is the usual method of using public key encryption
on large amounts of data, this is because public key encryption is slow
but symmetric encryption is fast. So symmetric encryption is used for
bulk encryption and the small random symmetric key used is transferred
using public key encryption.
.SH "SEE ALSO"
the \fIevp(3)|evp(3)\fR,the section on \fIrand(3)|rand(3)\fR manpage
the \fIEVP_EncryptInit(3)|EVP_EncryptInit(3)\fR manpage,
the \fIEVP_OpenInit(3)|EVP_OpenInit(3)\fR manpage
.SH "HISTORY"

.rn }` ''
.IX Title "EVP_SealInit 3"
.IX Name "EVP_SealInit, EVP_SealUpdate, EVP_SealFinal - EVP envelope encryption"

.IX Header "NAME"

.IX Header "SYNOPSIS"

.IX Header "DESCRIPTION"

.IX Header "RETURN VALUES"

.IX Header "NOTES"

.IX Header "SEE ALSO"

.IX Header "HISTORY"