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includefile(include/header)
COMMENT(manpage, section, releasedate, archive, short name)
manpage(FBB::OSymCryptStream)(3bobcat)(_CurYrs_)(libbobcat-dev__CurVers_)
(Symmetric en- and decryption)
manpagename(FBB::OSymCryptStream)(std::ostream performing symmetric
en/decryption)
manpagesynopsis()
bf(#include <bobcat/osymcryptstream>)nl()
Linking option: tt(-lbobcat -lcrypto)
manpagedescription()
bf(FBB::OSymCryptStream) objects can be used to encrypt or decrypt
information, that is available on separate tt(std::istream) streams.
The class tt(OSymCryptStream) is a class template, using a
tt(FBB::CryptType) template non-type parameter. Objects of the class
tt(FBB::OSymCryptStream<FBB::ENCRYPT>) encrypt the information they receive,
objects of the class tt(FBB::OSymCryptStream<FBB::DECRYPT>) decrypt the
information they receive.
All symmetric encryption methods defined by the OpenSSL library that can
be selected by name may be used to en/decrypt information. To select a
particular encryption method an identifier is passed to the constructor. E.g.,
tt("aes-256-gcm"). For the currently supported cipher algorithms issue the
command
verb(
openssl list -cipher-algorithms
)
tt(OSymCryptStream) objects read the information to en/decrypt from an
external source (e.g., from tt(std::istream) objects). The characters that
are encrypted or decrypted by tt(OSymCryptStream) objects are written to
tt(std::ostream) objects which are at construction-time specified as
tt(ostream) references or by filename.
includefile(include/namespace)
manpagesection(INHERITS FROM)
bf(FBB::OSymCryptStreambuf) (private), nl()
bf(std::istream)
manpagesection(CONSTRUCTORS)
itemization(
itb(OSymCryptStream<CryptType>(std::ostream &outStream,
std::string const &cipherName,
std::string const &key,
std::string const &iv,
size_t inBufSize = 100))
This constructor defines a tt(std::streambuf) encrypting or decrypting
the characters it receives.
- tt(OSymCryptStream<FBB::ENCRYPT>) objects perform encryption;nl()
tt(OSymCryptStream<FBB::DECRYPT>) objects perform decryption;
- tt(OSymCryptStream<CryptType>) objects write the encrypted or decrypted
characters to tt(outStream);nl()
- The encryption method to use is specified by the tt(cipherName)
parameter. E.g., tt("AES-256-GCM");nl()
- The symmetric key to use is specified by the tt(key) parameter;nl()
- The initialization vector is specified by the tt(iv) parameter;nl()
- The tt(FBB::OSymCryptStreambuf) internally used buffer will hold
tt(inBufSize) characters. The default value is the smallest value that
is used. When specifying a smaller tt(bufSize) value the default value
is used;nl()
itb(OSymCryptStream<CryptType>(std::string const &outStreamName,
std::string const &cipherName,
std::string const &key,
std::string const &iv,
size_t inBufSize = 100))
Same constructor as the previous one, but this constructor's first
parameter specifies the name of the file to receive the encrypted or
decrypted characters.
)
If the construction fails an exception is thrown, mentioning the openssl
function that failed to complete (see also tt(errorMsg) below).
The move constructor is available, the copy constructor and assignment
operators are not available,
manpagesection(INHERITED MEMBERS)
Since the class is publicly derived from bf(std::ostream), all
tt(std::ostream) members can be used.
manpagesection(MEMBER FUNCTIONS)
itemization(
itb(static std::string errorMsg())
If an openssl function fails an exception is thrown mentioning the
name of the failing function. In those cases the function tt(errorMsg) can be
called returning a tt(std::string) containing the openssl error code (returned
by tt(ERR_get_error)) and its textual representation (returned by
tt(ERR_error_string)). If the reported error code is zero, then in fact no
error has occurred and the exception was spuriously reported;
itb(static size_t keyLength(std::string const &cipherName))
returns the minimum key length required for cipher tt(cipherName);
itb(static size_t ivLength(std::sting const &cipherName))
returns the minimum length of the initialization vector that is
required for cipher tt(cipherName).
)
The latter two functions throw exceptions if tt(cipherName) does not
contain the name of a supported cipher algorithm.
manpagesection(MANIPULATOR)
itemization(
itb(std::ostream &FBB::eoi(std::ostream &out))
By inserting the tt(eoi) manipulator into an tt(OSymCryptStream) object
insertion is considered complete. It completes the insertion of
information into the tt(std::ostream) specified at construction time
as the tt(OSymCryptStream's) first argument. That way, you don't have
to wait until the tt(OSymCryptStream) object's destructor flushes that
stream. In the following example using the tt(eoi) manipulator is
illustrated in the (commented out lines near line 40): verb(
//in.seekg(0); // when activated, this won't
//enc << in.rdbuf(); // be processed due to '<< eoi'
)
Activating those lines will not result in processing the tt(in) stream
twice.
)
manpagesection(EXAMPLE)
verbinsert(-a ../../osymcryptstream/driver/driver.cc)
manpagefiles()
em(bobcat/osymcryptstream) - defines the class interface
manpageseealso()
bf(bobcat)(7),
bf(isymcryptstream)(3bobcat), bf(isymcryptstreambuf)(3bobcat),
bf(osymcryptstreambuf)(3bobcat)
manpagebugs()
None Reported.
includefile(include/trailer)
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