--- name: "isymcryptbuf" section: "3bobcat" platform: "linux" package: "libbobcat-dev" version: "5.07.00-1" release: "Debian 11 (Bullseye)" platforms: ["linux"] url: "https://new.carta.tech/isymcryptbuf" --- # isymcryptbuf(3bobcat) Input Filtering stream buffer doing symmetric encryption ## NAME FBB::ISymCryptStreambuf - Input Filtering stream buffer doing symmetric encryption ## SYNOPSIS **#include \**\ Linking option: *-lbobcat -lcrypto* ## DESCRIPTION The information made available by **ISymCryptStreambuf** objects has been subject to symmetric encryption or decryption. The information to be encrypted or decrypted is made available to **ISymCryptStreambuf** object via *std::istream* objects. The *class ISymCryptStreambuf* is a class template, using a *FBB::CryptType* template non-type parameter. Objects of the class *FBB::ISymCryptStreambuf\* encrypt the information they receive, objects of the class *FBB::ISymCryptStreambuf\* decrypt the information they receive. See also section **ENUMERATION** below. All symmetric encryption methods defined by the OpenSSL library that can be selected by name may be used in combination with *EncryptBuf* objects. To select a particular encryption method an identifier is passed to the constructor. E.g., *"aes-128-cbc"* indicating the AES (Rijndael) method, using 128 bit sized keys and blocks using \`cbc’ mode (see below for an explanation). 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 *’0’* characters). Most modes use an *initialization vector*. 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 *is* 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. Block ciphers use one of the following four encryption modes: - o **CBC (Cipher Block Chaining)**:\ 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. - o **ECB (Electronic Code Book)**:\ Each block is encrypted by itself, using the specified encryption method. Although an *initialization vector* 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. - o **CFB (Cipher Feednack)**:\ 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. - o **OFB (Output Feednack)**:\ 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. 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: | | | | | | | --- | --- | --- | --- | --- | | | | (bytes) | (bytes) | | | AES | 16 | 8 | CBC | "aes-128-cbc" | | | | | | CFB | "aes-128-cfb" | | | | | OFB | "aes-128-ofb" | | | 24 | 24 | CBC | "aes-192-cbc" | | | | | EBC | "aes-192-ecb" | | | | | CFB | "aes-192-cfb" | | | | | OFB | "aes-192-ofb" | | | 32 | 32 | CBC | "aes-256-cbc" | | | | | EBC | "aes-256-ecb" | | | | | CFB | "aes-256-cfb" | | | | | OFB | "aes-256-ofb" | | BLOWFISH | 16 | 8 | CBC | "bf-cbc" | | | | | EBC | "bf-ecb" | | | | | | OFB | "bf-ofb" | | max key length is 56 bytes, 16 generally used | | | CAMELLIA | 16 | 16 | CBC | "camellia-128-cbc" | | | | | EBC | "camellia-128-ecb" | | | | | | 24 | | CBC | "camellia-192-cbc" | | | | | EBC | "camellia-192-ecb" | | | | | CFB | "camellia-192-cfb" | | | | | OFB | "camellia-192-ofb" | | | 32 | | CBC | "camellia-256-cbc" | | | | | EBC | "camellia-256-ecb" | | | | | CFB | "camellia-256-cfb" | | | | | OFB | "camellia-256-ofb" | | CAST | 16 | 8 | CBC | "cast-cbc" | | | | | EBC | "cast-ecb" | | | | | CFB | "cast-cfb" | | | | | OFB | "cast-ofb" | | | DES | 8 | 8 | CBC | "des-cbc" | | | | | EBC | "des-ebc" | | | | | CFB | "des-cfb" | | | | | OFB | "des-ofb" | | DESX | | | | | | EBC | "des-ede" | | | | | CFB | "des-ede-cfb" | | | | | OFB | "des-ede-ofb" | | 3DES | 24 | 8 | CBC | "des-ede3-cbc" | | | | | | CFB | "des-ede3-cfb" | | | Key bytes 9-16 define the 2nd key, bytes 17-24 | | | define the 3rd key | | | RC2 | 16 | 8 | CBC | "rc2-cbc" | | | | | EBC | "rc2-ecb" | | | | | | OFB | "rc2-ofb" | | Key length variable, max. 128 bytes, default length is shown | | | RC2-40 | 5 | 8 | | "rc2-40-cbc" | | obsolete: avoid | | | RC2-64 | | obsolete: avoid | | | Key length is variable, max. 256 bytes. default length is shown | | | Encrypt again to decrypt. Don’t use *DecryptBuf* | | | RC4-40 | 5 | N.A. | | "rc4-40" | | obsolete: avoid | | | RC5 | | | | | | CFB | "rc5-cfb" | | | | | default # rounds is 12 | | | | The RC4 stream cipher is subject to a well-known attack (cf. http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Mantin1.zip) unless the initial 256 bytes produced by the cipher are discarded. ## NAMESPACE **FBB**\ All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace **FBB**. ## INHERITS FROM **FBB::IFilterBuf** ## MEMBER FUNCTIONS All members of **FBB::IFilterBuf** are available, as **ISymCryptStreambuf** inherits from this class. Overloaded move and/or copy assignment operators are not available. ## ENUMERATION **ISymCryptStreambuf** objects either encrypt or decrypt information. **ISymCryptStreambuf** objects of the class **FBB::ISymCryptStreambuf\** encrypt the data they receive, **ISymCryptStreambuf** objects of the class **FBB::ISymCryptStreambuf\** decrypt the data they receive. The values *ENCRYPT* and *DECRYPT* are defined in the *enum CryptType*, which is defined in the *FBB* namespace. ## CONSTRUCTOR - o **ISymCryptStreambuf\(** **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)**:\ This constructor initializes the streambuf. - *ISymCryptStreambuf\* objects perform encryption;\ *ISymCryptStreambuf\* objects perform decryption;\ \- *ISymCryptStreambuf\* objects obtain the bytes to encrypt or decrypt from *std::istream &in*;\ \- The encryption method to use is specified by the *type* parameter. E.g., *"bf-cbc"* selects the Blowfish Cipher Block Chaining method;\ \- The symmetric key to use is specified by the *key* parameter;\ \- The initialization vector is specified by the *iv* parameter;\ \- The *FBB::ISymCryptStreambuf* internally used buffer will contain *bufSize* characters. The default value is the smallest value that is used. When a smaller *bufSize* value is specified, the default value is used;\ \- *FBB::ISymCryptStreambuf*’s *IFilterBuf* base class is initialized with a buffer of size *filterBufSize*, using a lower bound of 100;\ \- The parameter *ENGINE* 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. Copy and move constructors (and assignment operators) are not available. ## EXAMPLE The example shows the construction of an *ISymCryptStreambuf\* object *ebuf* which is used to initialize a *std::istream* object. The information read from this *istream* is encrypted using the Blowfish CBC method. A *ISymCryptStreambuf\* object (*dbuf* reads the information from that stream and decrypts it again). The *std::istream din* object is initialized with the *ISymCryptStreambuf\* object, and its content is sent to *std::cout*. The information that is presented at *std::cin* and that appears at *std::cout* should be identical. ``` #include #include using namespace std; using namespace FBB; int main() { ISymCryptStreambuf ebuf(cin, "bf-cbc", "1234567890", "1234567890"); istream ein(&ebuf); ISymCryptStreambuf dbuf(ein, "bf-cbc", "1234567890", "1234567890"); istream din(&dbuf); cout << din.rdbuf(); } ``` ## FILES *bobcat/isymcryptstreambuf* - defines the class interface ## SEE ALSO [**bobcat**(7)](/bobcat/7.md), [**encryptbuf**(3bobcat)](/encryptbuf/3bobcat.md), [**isymcryptstream**(3bobcat)](/isymcryptstream/3bobcat.md), [**ibase64buf**(3bobcat)](/ibase64buf/3bobcat.md), [**ifilterbuf**(3bobcat)](/ifilterbuf/3bobcat.md), [**ofilterbuf**(3bobcat)](/ofilterbuf/3bobcat.md), **std::streambuf**. ## BUGS Sep/Oct 2013: due to a change in library handling by the linker (cf. http://fedoraproject.org/wiki/UnderstandingDSOLinkChange and https://wiki.debian.org/ToolChain/DSOLinking) libraries that are indirectly required are no longer automatically linked to your program. With **BigInt** this is *libcrypto*, which requires programs to link to both *bobcat* and *crypto*. ## BOBCAT PROJECT FILES - o *https://fbb-git.gitlab.io/bobcat/*: gitlab project page; - o *bobcat\_5.07.00-x.dsc*: detached signature; - o *bobcat\_5.07.00-x.tar.gz*: source archive; - o *bobcat\_5.07.00-x\_i386.changes*: change log; - o *libbobcat1\_5.07.00-x\_\*.deb*: debian package containing the libraries; - o *libbobcat1-dev\_5.07.00-x\_\*.deb*: debian package containing the libraries, headers and manual pages; ## BOBCAT Bobcat is an acronym of \`Brokken’s Own Base Classes And Templates’. ## COPYRIGHT This is free software, distributed under the terms of the GNU General Public License (GPL). ## AUTHOR Frank B. Brokken (**f.b.brokken@rug.nl**).