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<h1 id="title">FBB::ISymCryptStreambuf</h1>
<h2 id="author">libbobcat-dev_4.04.00-x.tar.gz</h2>
<h2 id="date">2005-2016</h2>
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<h1 id="title">FBB::ISymCryptStreambuf(3bobcat)</h1>
<h2 id="author">libbobcat-dev_4.04.00-x.tar.gz Symmetric Encryption Stream Buffer</h2>
<h2 id="date">2005-2016</h2>
<p>
<h2 >NAME</h2>FBB::ISymCryptStreambuf - Input Filtering stream buffer doing symmetric encryption
<p>
<h2 >SYNOPSIS</h2>
<strong >#include <bobcat/isymcryptstreambuf></strong><br/>
Linking option: <em >-lbobcat -lcrypto</em>
<p>
<h2 >DESCRIPTION</h2>
The information made available by <strong >ISymCryptStreambuf</strong> objects has
been subject to symmetric encryption or decryption. The information to be
encrypted or decrypted is made available to <strong >ISymCryptStreambuf</strong> object
via <em >std::istream</em> objects.
<p>
The <em >class ISymCryptStreambuf</em> is a class template, using a
<em >FBB::CryptType</em> template non-type parameter. Objects of the class
<em >FBB::ISymCryptStreambuf<FBB::ENCRYPT></em> encrypt the information they
receive, objects of the class <em >FBB::ISymCryptStreambuf<FBB::DECRYPT></em>
decrypt the information they receive. See also section <strong >ENUMERATION</strong> below.
<p>
All symmetric encryption methods defined by the OpenSSL library that can
be selected by name may be used in combination with <em >EncryptBuf</em> objects. To
select a particular encryption method an identifier is passed to the
constructor. E.g., <em >"aes-128-cbc"</em> indicating the AES (Rijndael) method,
using 128 bit sized keys and blocks using `cbc' mode (see below for an
explanation).
<p>
When providing shorter keys than expected by the method the provided key
is extended by adding the required number of 0-bytes. (zero valued bytes,
not <em >'0'</em> characters).
<p>
Most modes use an <em >initialization vector</em>. The initialization vector must be
provided at construction time. The matching decrypting object needs to know
the initialization vector that was used when encrypting the data: the
application must ensure that the matching decryption object receives the same
initialization vector as the one that was provided to the encryption
object. Initialization vectors are not security sensitive in the sense that
they can be sent in the clear to the decryption object. What <em >is</em>
important, though, is that they contain random data when used `for real'. When
an initialization vector is specified that is shorter than expected by the
method it will be extended with the required number of 0-bytes.
<p>
Block ciphers use one of the following four encryption modes:
<ul>
<li> <strong >CBC (Cipher Block Chaining)</strong>:<br/>
The first block is XOR-ed by the initialization vector and then
encrypted using the specified method. Subsequent blocks are XOR-ed by the
encrypted version of the preceding block. Due to the initialization vector
dictionary attacks are infeasible, as long as the initialization vector is
truly random.
<li> <strong >ECB (Electronic Code Book)</strong>:<br/>
Each block is encrypted by itself, using the specified encryption
method. Although an <em >initialization vector</em> may be specified, it is not
used. This method is susceptible to dictionary attacks and should therefore be
avoided, unless you know what you're doing.
<li> <strong >CFB (Cipher Feednack)</strong>:<br/>
This method allows a block cipher to be used as a stream cipher. It
uses an initialization vector, which should be unique and random for each new
stream of data that is encrypted using the method. Encryption can only start
after the first data block has been received.
<li> <strong >OFB (Output Feednack)</strong>:<br/>
This is an alternative way to use a block cipher as a stream
cipher. It is somewhat more susceptible to traditional data manipulation
attacks, which can usually be thwarted when a message authentication code is
added to the information as well. Like CFB it uses an initialization vector,
which should again be unique and random for each new stream of data that is
encrypted.
</ul>
<p>
The following table presents an overview of methods that are currently
available. Methods for which the block size is specified as N.A. are stream
ciphers; other methods are block ciphers:
<table>
<td colspan=5><hr/></td>
<tr >
<td > method</td><td > keysize</td><td > blocksize</td><td > mode</td><td > identifier</td>
</tr>
<tr >
<td > </td><td > (bytes)</td><td > (bytes)</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > AES</td><td > 16</td><td > 8</td><td > CBC</td><td > "aes-128-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "aes-128-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "aes-128-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "aes-128-ofb"</td>
</tr>
<tr >
<td > </td><td > 24</td><td > 24</td><td > CBC</td><td > "aes-192-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "aes-192-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "aes-192-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "aes-192-ofb"</td>
</tr>
<tr >
<td > </td><td > 32</td><td > 32</td><td > CBC</td><td > "aes-256-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "aes-256-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "aes-256-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "aes-256-ofb"</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > BLOWFISH</td><td > 16</td><td > 8</td><td > CBC</td><td > "bf-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "bf-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "bf-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "bf-ofb"</td>
</tr>
<tr >
<td > max key length is 56 bytes, 16 generally used</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > CAMELLIA</td><td > 16</td><td > 16</td><td > CBC</td><td > "camellia-128-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "camellia-128-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "camellia-128-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "camellia-128-ofb"</td>
</tr>
<tr >
<td > </td><td > 24</td><td > </td><td > CBC</td><td > "camellia-192-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "camellia-192-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "camellia-192-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "camellia-192-ofb"</td>
</tr>
<tr >
<td > </td><td > 32</td><td > </td><td > CBC</td><td > "camellia-256-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "camellia-256-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "camellia-256-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "camellia-256-ofb"</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > CAST</td><td > 16</td><td > 8</td><td > CBC</td><td > "cast-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "cast-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "cast-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "cast-ofb"</td>
</tr>
<tr >
<td > min key length is 5 bytes, max is shown</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > DES</td><td > 8</td><td > 8</td><td > CBC</td><td > "des-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "des-ebc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "des-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "des-ofb"</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > DESX</td><td > 8</td><td > 8</td><td > CBC</td><td > "desx-cbc"</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > 3DES</td><td > 16</td><td > 8</td><td > CBC</td><td > "des-ede-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "des-ede"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "des-ede-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "des-ede-ofb"</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > 3DES</td><td > 24</td><td > 8</td><td > CBC</td><td > "des-ede3-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "des-ede3"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "des-ede3-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "des-ede3-ofb"</td>
</tr>
<tr >
<td > Key bytes 9-16 define the 2nd key, bytes 17-24</td>
</tr>
<tr >
<td > define the 3rd key</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > RC2</td><td > 16</td><td > 8</td><td > CBC</td><td > "rc2-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "rc2-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "rc2-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "rc2-ofb"</td>
</tr>
<tr >
<td > Key length variable, max. 128 bytes, default length is shown</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > RC2-40</td><td > 5</td><td > 8</td><td > </td><td > "rc2-40-cbc"</td>
</tr>
<tr >
<td > obsolete: avoid</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > RC2-64</td><td > 8</td><td > 8</td><td > </td><td > "rc2-64-cbc"</td>
</tr>
<tr >
<td > obsolete: avoid</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > RC4</td><td > 16</td><td > N.A.</td><td > </td><td > "rc4"</td>
</tr>
<tr >
<td > Key length is variable, max. 256 bytes. default length is shown</td>
</tr>
<tr >
<td > Encrypt again to decrypt. Don't use <em >DecryptBuf</em></td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > RC4-40</td><td > 5</td><td > N.A.</td><td > </td><td > "rc4-40"</td>
</tr>
<tr >
<td > obsolete: avoid</td>
</tr>
<td colspan=5><hr/></td>
<tr >
<td > RC5</td><td > 16</td><td > 8</td><td > CBC</td><td > "rc5-cbc"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > EBC</td><td > "rc5-ecb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > CFB</td><td > "rc5-cfb"</td>
</tr>
<tr >
<td > </td><td > </td><td > </td><td > OFB</td><td > "rc5-ofb"</td>
</tr>
<tr >
<td > Key length variable, max. 256 bytes, rounds 8, 12 or 16,</td>
</tr>
<tr >
<td > default # rounds is 12</td>
</tr>
<td colspan=5><hr/></td>
</table>
<p>
The RC4 stream cipher is subject to a well-known attack
(cf. <a href="http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Mantin1.zip">http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Mantin1.zip</a>)
unless the initial 256 bytes produced by the cipher are discarded.
<p>
<h2 >NAMESPACE</h2>
<strong >FBB</strong><br/>
All constructors, members, operators and manipulators, mentioned in this
man-page, are defined in the namespace <strong >FBB</strong>.
<p>
<h2 >INHERITS FROM</h2>
<strong >FBB::IFilterStreambuf</strong>
<p>
<h2 >MEMBER FUNCTIONS</h2>
All members of <strong >FBB::IFilterStreambuf</strong> are available, as
<strong >ISymCryptStreambuf</strong> inherits from this class.
<p>
Overloaded move and/or copy assignment operators are not available.
<p>
<h2 >ENUMERATION</h2>
<p>
<strong >ISymCryptStreambuf</strong> objects either encrypt or decrypt
information. <strong >ISymCryptStreambuf</strong> objects of the class
<strong >FBB::ISymCryptStreambuf<FBB::ENCRYPT></strong> encrypt the data they receive,
<strong >ISymCryptStreambuf</strong> objects of the class
<strong >FBB::ISymCryptStreambuf<FBB::DECRYPT></strong> decrypt the data they receive.
<p>
The values <em >ENCRYPT</em> and <em >DECRYPT</em> are defined in the <em >enum CryptType</em>,
which is defined in the <em >FBB</em> namespace.
<p>
<h2 >CONSTRUCTOR</h2>
<ul>
<li> <strong >ISymCryptStreambuf<CryptType>(
std::istream &in, char const *type,
std::string const &key, std::string const &iv,
size_t bufSize = 100, size_t filterBufSize = 1000,
ENGINE *engine = 0)</strong>:<br/>
This constructor initializes the streambuf.
<ul>
- <em >ISymCryptStreambuf<ENCRYPT></em> objects perform encryption;<br/>
<em >ISymCryptStreambuf<DECRYPT></em> objects perform decryption;<br/>
- <em >ISymCryptStreambuf<CryptType></em> objects obtain the bytes to encrypt
or decrypt from <em >std::istream &in</em>;<br/>
- The encryption method to use is specified by the <em >type</em>
parameter. E.g., <em >"bf-cbc"</em> selects the Blowfish Cipher Block Chaining
method;<br/>
- The symmetric key to use is specified by the <em >key</em> parameter;<br/>
- The initialization vector is specified by the <em >iv</em> parameter;<br/>
- The <em >FBB::ISymCryptStreambuf</em> internally used buffer will contain
<em >bufSize</em> characters. The default value is the smallest value that is
used. When a smaller <em >bufSize</em> value is specified, the default value is
used;<br/>
- <em >FBB::ISymCryptStreambuf</em>'s <em >IFilterStreambuf</em> base class is
initialized with a buffer of size <em >filterBufSize</em>, using a lower bound
of 100;<br/>
- The parameter <em >ENGINE</em> can be used to specify a hardware
acceleration engine, as supported by the used encryption/decryption
method. Its default argument value indicates that no hardware acceleration is
available.
</ul>
</ul>
Copy- and move constructors are not available.
<p>
<h2 >EXAMPLE</h2>
<p>
The example shows the construction of an <em >ISymCryptStreambuf<ENCRYPT></em>
object <em >ebuf</em> which is used to initialize a <em >std::istream</em> object. The
information read from this <em >istream</em> is encrypted using the Blowfish CBC
method. A <em >ISymCryptStreambuf<DECRYPT></em> object (<em >dbuf</em> reads the
information from that stream and decrypts it again). The <em >std::istream din</em>
object is initialized with the <em >ISymCryptStreambuf<DECRYPT></em> object, and its
contents is sent to <em >std::cout</em>. The information that is presented at
<em >std::cin</em> and that appears at <em >std::cout</em> should be identical.
<p>
<pre >
#include <iostream>
#include <bobcat/isymcryptstreambuf>
using namespace std;
using namespace FBB;
int main()
{
ISymCryptStreambuf<ENCRYPT> ebuf(cin, "bf-cbc",
"1234567890", "1234567890");
istream ein(&ebuf);
ISymCryptStreambuf<DECRYPT> dbuf(ein, "bf-cbc",
"1234567890", "1234567890");
istream din(&dbuf);
cout << din.rdbuf();
}
</pre>
<p>
<h2 >FILES</h2>
<em >bobcat/isymcryptstreambuf</em> - defines the class interface
<p>
<h2 >SEE ALSO</h2>
<strong >bobcat</strong>(7), <strong >encryptbuf</strong>(3bobcat), <strong >isymcryptstream</strong>(3bobcat),
<strong >ibase64streambuf</strong>(3bobcat), <strong >ifilterstreambuf</strong>(3bobcat),
<strong >ofilterstreambuf</strong>(3bobcat), <strong >std::streambuf</strong>.
<p>
<h2 >BUGS</h2>
<p>
Sep/Oct 2013: due to a change in library handling by the linker
(cf. <a href="http://fedoraproject.org/wiki/UnderstandingDSOLinkChange">http://fedoraproject.org/wiki/UnderstandingDSOLinkChange</a> and
<a href="https://wiki.debian.org/ToolChain/DSOLinking">https://wiki.debian.org/ToolChain/DSOLinking</a>) libraries that are
indirectly required are no longer automatically linked to your program. With
<strong >BigInt</strong> this is <em >libcrypto</em>, which requires programs to link to both
<em >bobcat</em> and <em >crypto</em>.
<p>
<h2 >DISTRIBUTION FILES</h2>
<ul>
<li> <em >bobcat_4.04.00-x.dsc</em>: detached signature;
<li> <em >bobcat_4.04.00-x.tar.gz</em>: source archive;
<li> <em >bobcat_4.04.00-x_i386.changes</em>: change log;
<li> <em >libbobcat1_4.04.00-x_*.deb</em>: debian package holding the
libraries;
<li> <em >libbobcat1-dev_4.04.00-x_*.deb</em>: debian package holding the
libraries, headers and manual pages;
<li> <em >http://sourceforge.net/projects/bobcat</em>: public archive location;
</ul>
<p>
<h2 >BOBCAT</h2>
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.
<p>
<h2 >COPYRIGHT</h2>
This is free software, distributed under the terms of the
GNU General Public License (GPL).
<p>
<h2 >AUTHOR</h2>
Frank B. Brokken (<strong >f.b.brokken@rug.nl</strong>).
<p>
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