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.\" $OpenBSD: EVP_rc2_cbc.3,v 1.1 2024/12/08 17:41:23 schwarze Exp $
.\"
.\" Copyright (c) 2024 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: December 8 2024 $
.Dt EVP_RC2_CBC 3
.Os
.Sh NAME
.Nm EVP_rc2_cbc ,
.Nm EVP_rc2_ecb ,
.Nm EVP_rc2_cfb64 ,
.Nm EVP_rc2_cfb ,
.Nm EVP_rc2_ofb ,
.Nm EVP_rc2_40_cbc ,
.Nm EVP_rc2_64_cbc
.Nd Rivest Cipher 2 in the EVP framework
.Sh SYNOPSIS
.In openssl/evp.h
.Ft const EVP_CIPHER *
.Fn EVP_rc2_cbc void
.Ft const EVP_CIPHER *
.Fn EVP_rc2_ecb void
.Ft const EVP_CIPHER *
.Fn EVP_rc2_cfb64 void
.Ft const EVP_CIPHER *
.Fn EVP_rc2_cfb void
.Ft const EVP_CIPHER *
.Fn EVP_rc2_ofb void
.Ft const EVP_CIPHER *
.Fn EVP_rc2_40_cbc void
.Ft const EVP_CIPHER *
.Fn EVP_rc2_64_cbc void
.In openssl/rc2.h
.Fd #define RC2_BLOCK 8
.Fd #define RC2_KEY_LENGTH 16
.Sh DESCRIPTION
RC2 is a block cipher operating on blocks of
.Dv RC2_BLOCK No = 8
bytes, equivalent to 64 bits, using a variable
.Fa key
length with an additional parameter called
.Dq effective key bits
or
.Dq effective key length .
.Pp
.Fn EVP_rc2_cbc ,
.Fn EVP_rc2_ecb ,
.Fn EVP_rc2_cfb64 ,
and
.Fn EVP_rc2_ofb
provide the RC2 encryption algorithm in CBC, ECB, CFB and OFB mode,
respectively.
.Fn EVP_rc2_cfb
is an alias for
.Fn EVP_rc2_cfb64 ,
implemented as a macro.
.Pp
By default, these functions set both the key length
and the effective key length to
.Dv RC2_KEY_LENGTH No = 16
bytes, which is not a very useful value because it is quite short.
.Pp
Configuring normally requires a multi-step process:
.Bl -enum -width 2n
.It
Create a new, empty
.Vt EVP_CIPHER_CTX
object with
.Xr EVP_CIPHER_CTX_new 3 .
.It
Select the operation mode by calling
.Xr EVP_EncryptInit 3
with the desired
.Fa type
argument, passing
.Dv NULL
pointers for the
.Fa key
and
.Fa iv
arguments.
.It
Select the
.Fa key
length by passing the desired number of bytes to
.Xr EVP_CIPHER_CTX_set_key_length 3 .
Doing so overrides the default key length of
.Dv RC2_KEY_LENGTH No = 16 .
Valid values for
.Fa keylen
are positive and less than or equal to 128.
.It
Select the effective key length by calling
.Xr EVP_CIPHER_CTX_ctrl 3
with a
.Fa type
argument of
.Dv EVP_CTRL_SET_RC2_KEY_BITS ,
passing the desired number of bits in
.Fa arg .
Doing so overrides the default effective key length of 128 bits.
Valid values for
.Fa arg
are positive and less than or equal to 1024.
The
.Fa ptr
argument is ignored; passing
.Dv NULL
is recommended.
.It
Call
.Xr EVP_EncryptInit 3
a second time, this time passing
.Dv NULL
for the type argument.
The
.Fa key
argument points to an array containing the number of bytes that was passed to
.Xr EVP_CIPHER_CTX_set_key_length 3 ,
and the
.Fa iv
argument points to an array of eight bytes.
.It
Finally,
.Xr EVP_EncryptUpdate 3
and
.Xr EVP_EncryptFinal 3
can be used in the normal way.
.El
.Pp
Once a
.Fa ctx
object is fully configured, calling
.Xr EVP_CIPHER_CTX_ctrl 3
with a
.Fa type
argument of
.Dv EVP_CTRL_GET_RC2_KEY_BITS
interprets
.Fa ptr
as a pointer to
.Vt int
and stores the effective key length in bits at that location.
In this case,
.Fa arg
is ignored and passing 0 is recommended.
.Pp
In the CFB and OFB modes, the minimum required total length in bytes
of the output buffer is equal to the total number of input bytes to
be encoded.
In the CBC and ECB modes, the minimum required total length
of the output buffer has to be rounded up to the next multiple
of the block size of eight bytes.
.Pp
.Fn EVP_rc2_40_cbc
and
.Fn EVP_rc2_64_cbc
are obsolete functions that provide the RC2 algorithm in CBC mode
with a key length and an effective key length of 40 and 64 bits,
respectively.
.Sh RETURN VALUES
With the
.Vt EVP_CIPHER
objects documented in the present manual page,
.Fn EVP_CIPHER_CTX_ctrl
returns 1 for success or 0 if an error occurs.
.Sh SEE ALSO
.Xr evp 3 ,
.Xr EVP_CIPHER_CTX_set_key_length 3 ,
.Xr EVP_EncryptInit 3 ,
.Xr RC2_encrypt 3
.Sh HISTORY
.Fn EVP_rc2_cbc ,
.Fn EVP_rc2_ecb ,
.Fn EVP_rc2_cfb ,
and
.Fn EVP_rc2_ofb
first appeared in SSLeay 0.5.2 and have been available since
.Ox 2.4 .
.Pp
.Fn EVP_rc2_40_cbc
and
.Fn EVP_rc2_64_cbc
first appeared in SSLeay 0.9.1 and have been available since
.Ox 2.6 .
.Pp
.Fn EVP_rc2_cfb64
first appeared in OpenSSL 0.9.7e and has been available since
.Ox 3.8 .
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