- update OpenSSL to 0.9.8
[dragonfly.git] / secure / lib / libcrypto / man / EVP_SealInit.3
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129.\" ========================================================================
130.\"
131.IX Title "EVP_SealInit 3"
a561f9ff 132.TH EVP_SealInit 3 "2005-07-06" "0.9.8" "OpenSSL"
984263bc 133.SH "NAME"
74dab6c2 134EVP_SealInit, EVP_SealUpdate, EVP_SealFinal \- EVP envelope encryption
984263bc 135.SH "SYNOPSIS"
8b0cefbb 136.IX Header "SYNOPSIS"
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137.Vb 1
138\& #include <openssl/evp.h>
139.Ve
8b0cefbb 140.PP
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141.Vb 7
142\& int EVP_SealInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
143\& unsigned char **ek, int *ekl, unsigned char *iv,
144\& EVP_PKEY **pubk, int npubk);
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145\& int EVP_SealUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
146\& int *outl, unsigned char *in, int inl);
147\& int EVP_SealFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
148\& int *outl);
149.Ve
150.SH "DESCRIPTION"
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151.IX Header "DESCRIPTION"
152The \s-1EVP\s0 envelope routines are a high level interface to envelope
153encryption. They generate a random key and \s-1IV\s0 (if required) then
154\&\*(L"envelope\*(R" it by using public key encryption. Data can then be
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155encrypted using this key.
156.PP
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157\&\fIEVP_SealInit()\fR initializes a cipher context \fBctx\fR for encryption
158with cipher \fBtype\fR using a random secret key and \s-1IV\s0. \fBtype\fR is normally
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159supplied by a function such as \fIEVP_des_cbc()\fR. The secret key is encrypted
160using one or more public keys, this allows the same encrypted data to be
161decrypted using any of the corresponding private keys. \fBek\fR is an array of
162buffers where the public key encrypted secret key will be written, each buffer
163must contain enough room for the corresponding encrypted key: that is
8b0cefbb 164\&\fBek[i]\fR must have room for \fBEVP_PKEY_size(pubk[i])\fR bytes. The actual
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165size of each encrypted secret key is written to the array \fBekl\fR. \fBpubk\fR is
166an array of \fBnpubk\fR public keys.
167.PP
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168The \fBiv\fR parameter is a buffer where the generated \s-1IV\s0 is written to. It must
169contain enough room for the corresponding cipher's \s-1IV\s0, as determined by (for
170example) EVP_CIPHER_iv_length(type).
984263bc 171.PP
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172If the cipher does not require an \s-1IV\s0 then the \fBiv\fR parameter is ignored
173and can be \fB\s-1NULL\s0\fR.
984263bc 174.PP
8b0cefbb 175\&\fIEVP_SealUpdate()\fR and \fIEVP_SealFinal()\fR have exactly the same properties
984263bc 176as the \fIEVP_EncryptUpdate()\fR and \fIEVP_EncryptFinal()\fR routines, as
8b0cefbb 177documented on the \fIEVP_EncryptInit\fR\|(3) manual
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178page.
179.SH "RETURN VALUES"
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180.IX Header "RETURN VALUES"
181\&\fIEVP_SealInit()\fR returns 0 on error or \fBnpubk\fR if successful.
984263bc 182.PP
8b0cefbb 183\&\fIEVP_SealUpdate()\fR and \fIEVP_SealFinal()\fR return 1 for success and 0 for
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184failure.
185.SH "NOTES"
8b0cefbb 186.IX Header "NOTES"
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187Because a random secret key is generated the random number generator
188must be seeded before calling \fIEVP_SealInit()\fR.
189.PP
8b0cefbb 190The public key must be \s-1RSA\s0 because it is the only OpenSSL public key
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191algorithm that supports key transport.
192.PP
193Envelope encryption is the usual method of using public key encryption
194on large amounts of data, this is because public key encryption is slow
195but symmetric encryption is fast. So symmetric encryption is used for
196bulk encryption and the small random symmetric key used is transferred
197using public key encryption.
198.PP
199It is possible to call \fIEVP_SealInit()\fR twice in the same way as
8b0cefbb 200\&\fIEVP_EncryptInit()\fR. The first call should have \fBnpubk\fR set to 0
984263bc 201and (after setting any cipher parameters) it should be called again
8b0cefbb 202with \fBtype\fR set to \s-1NULL\s0.
984263bc 203.SH "SEE ALSO"
74dab6c2 204.IX Header "SEE ALSO"
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205\&\fIevp\fR\|(3), \fIrand\fR\|(3),
206\&\fIEVP_EncryptInit\fR\|(3),
207\&\fIEVP_OpenInit\fR\|(3)
208.SH "HISTORY"
984263bc 209.IX Header "HISTORY"
8b0cefbb 210\&\fIEVP_SealFinal()\fR did not return a value before OpenSSL 0.9.7.