NAME
DESrandomkey, DESsetkey, DESkeysched, DESsetkeychecked, DESsetkeyunchecked, DESsetoddparity, DESisweakkey, DESecbencrypt, DESecb2encrypt, DESecb3encrypt, DESncbcencrypt, DEScfbencrypt, DESofbencrypt, DESpcbcencrypt, DEScfb64encrypt, DESofb64encrypt, DESxcbcencrypt, DESede2cbcencrypt, DESede2cfb64encrypt, DESede2ofb64encrypt, DESede3cbcencrypt, DESede3cbcmencrypt, DESede3cfb64encrypt, DESede3ofb64encrypt, DEScbccksum, DESquadcksum, DESstringtokey, DESstringto2keys,DESfcrypt, DEScrypt, DESencread, DESencwrite - DES encryption
SYNOPSIS
#include
void DESrandomkey(DEScblock *ret); int DESsetkey(constDEScblock *key, DESkeyschedule *schedule); int DESkeysched(constDEScblock *key, DESkeyschedule *schedule); int DESsetkeychecked(constDEScblock *key, DESkeyschedule *schedule); void DESsetkeyunchecked(constDEScblock *key, DESkeyschedule *schedule); void DESsetoddparity(DEScblock *key); int DESisweakkey(constDEScblock *key); void DESecbencrypt(constDEScblock *input, DEScblock *output, DESkeyschedule *ks, int enc); void DESecb2encrypt(constDEScblock *input, DEScblock *output, DESkeyschedule *ks1, DESkeyschedule *ks2, int enc); void DESecb3encrypt(constDEScblock *input, DEScblock *output, DESkeyschedule *ks1, DESkeyschedule *ks2, DESkeyschedule *ks3, int enc); void DESncbcencrypt(const unsigned char *input, unsigned char *output, long length, DESkeyschedule *schedule, DEScblock *ivec, int enc); void DEScfbencrypt(const unsigned char *in, unsigned char *out, int numbits, long length, DESkeyschedule *schedule, DEScblock *ivec, int enc); void DESofbencrypt(const unsigned char *in, unsigned char *out, int numbits, long length, DESkeyschedule *schedule, DEScblock *ivec); void DESpcbcencrypt(const unsigned char *input, unsigned char *output, long length, DESkeyschedule *schedule, DEScblock *ivec, int enc); void DEScfb64encrypt(const unsigned char *in, unsigned char *out, long length, DESkeyschedule *schedule, DEScblock *ivec, int *num, int enc); void DESofb64encrypt(const unsigned char *in, unsigned char *out, long length, DESkeyschedule *schedule, DEScblock *ivec, int *num); void DESxcbcencrypt(const unsigned char *input, unsigned char *output, long length, DESkeyschedule *schedule, DEScblock *ivec, constDEScblock *inw, constDEScblock *outw, int enc); void DESede2cbcencrypt(const unsigned char *input, unsigned char *output, long length, DESkeyschedule *ks1, DESkeyschedule *ks2, DEScblock *ivec, int enc); void DESede2cfb64encrypt(const unsigned char *in, unsigned char *out, long length, DESkeyschedule *ks1, DESkeyschedule *ks2, DEScblock *ivec, int *num, int enc); void DESede2ofb64encrypt(const unsigned char *in, unsigned char *out, long length, DESkeyschedule *ks1, DESkeyschedule *ks2, DEScblock *ivec, int *num); void DESede3cbcencrypt(const unsigned char *input, unsigned char *output, long length, DESkeyschedule *ks1, DESkeyschedule *ks2, DESkeyschedule *ks3, DEScblock *ivec, int enc); void DESede3cbcmencrypt(const unsigned char *in, unsigned char *out, long length, DESkeyschedule *ks1, DESkeyschedule *ks2, DESkeyschedule *ks3, DEScblock *ivec1, DEScblock *ivec2, int enc); void DESede3cfb64encrypt(const unsigned char *in, unsigned char *out, long length, DESkeyschedule *ks1, DESkeyschedule *ks2, DESkeyschedule *ks3, DEScblock *ivec, int *num, int enc); void DESede3ofb64encrypt(const unsigned char *in, unsigned char *out, long length, DESkeyschedule *ks1, DESkeyschedule *ks2, DESkeyschedule *ks3, DEScblock *ivec, int *num); DESLONG DEScbccksum(const unsigned char *input, DEScblock *output, long length, DESkeyschedule *schedule, constDEScblock *ivec); DESLONG DESquadcksum(const unsigned char *input, DEScblock output[], long length, int outcount, DEScblock *seed); void DESstringtokey(const char *str, DEScblock *key); void DESstringto2keys(const char *str, DEScblock *key1, DEScblock *key2); char *DESfcrypt(const char *buf, const char *salt, char *ret); char *DEScrypt(const char *buf, const char *salt); int DESencread(int fd, void *buf, int len, DESkeyschedule *sched, DEScblock *iv); int DESencwrite(int fd, const void *buf, int len, DESkeyschedule *sched, DEScblock *iv);DESCRIPTION
This library contains a fast implementation of the DES encryption algorithm. There are two phases to the use of DES encryption. The first is the generation of a DESkeyschedule from a key, the second is the actual encryption. A DES key is of type DEScblock. This type is consists of 8 bytes with odd parity. The least significant bit in each byte is the parity bit. The key schedule is an expanded form of the key; it is used to speed the encryption process. DESrandomkey() generates a random key. The PRNG must be seeded prior to using this function (see rand(3)). If the PRNG could not generate a secure key, 0 is returned. Before a DES key can be used, it must be converted into the architecture dependent DESkeyschedule via the DESsetkeychecked() or DESsetkeyunchecked() function. DESsetkeychecked() will check that the key passed is of odd parityand is not a week or semi-weak key. If the parity is wrong, then -1 is
returned. If the key is a weak key, then -2 is returned. If an error
is returned, the key schedule is not generated. DESsetkey() works like DESsetkeychecked() if the DEScheckkeyflag is non-zero, otherwise like DESsetkeyunchecked(). These
functions are available for compatibility; it is recommended to use a function that does not depend on a global variable. DESsetoddparity() sets the parity of the passed key to odd. DESisweakkey() returns 1 is the passed key is a weak key, 0 if it is ok. The probability that a randomly generated key is weak is 1/2^52, so it is not really worth checking for them. The following routines mostly operate on an input and output stream of DEScblocks. DESecbencrypt() is the basic DES encryption routine that encrypts ordecrypts a single 8-byte DEScblock in electronic code book (ECB) mode.
It always transforms the input data, pointed to by input, into the output data, pointed to by the output argument. If the encryptargument is non-zero (DESENCRYPT), the input (cleartext) is encrypted
in to the output (ciphertext) using the keyschedule specified by the schedule argument, previously set via DESsetkey. If encrypt is zero (DESDECRYPT), the input (now ciphertext) is decrypted into the output (now cleartext). Input and output may overlap. DESecbencrypt() does not return a value.DESecb3encrypt() encrypts/decrypts the input block by using three-key
Triple-DES encryption in ECB mode. This involves encrypting the input
with ks1, decrypting with the key schedule ks2, and then encrypting with ks3. This routine greatly reduces the chances of brute force breaking of DES and has the advantage of if ks1, ks2 and ks3 are the same, it is equivalent to just encryption using ECB mode and ks1 as the key.The macro DESecb2encrypt() is provided to perform two-key Triple-DES
encryption by using ks1 for the final encryption.DESncbcencrypt() encrypts/decrypts using the cipher-block-chaining
(CBC) mode of DES. If the encrypt argument is non-zero, the routine
cipher-block-chain encrypts the cleartext data pointed to by the input
argument into the ciphertext pointed to by the output argument, using the key schedule provided by the schedule argument, and initialization vector provided by the ivec argument. If the length argument is not an integral multiple of eight bytes, the last block is copied to a temporary area and zero filled. The output is always an integral multiple of eight bytes. DESxcbcencrypt() is RSA's DESX mode of DES. It uses inw and outw to 'whiten' the encryption. inw and outw are secret (unlike the iv) and are as such, part of the key. So the key is sort of 24 bytes. This is much better than CBC DES. DESede3cbcencrypt() implements outer triple CBC DES encryption with three keys. This means that each DES operation inside the CBC mode is really an "C=E(ks3,D(ks2,E(ks1,M)))". This mode is used by SSL.The DESede2cbcencrypt() macro implements two-key Triple-DES by
reusing ks1 for the final encryption. "C=E(ks1,D(ks2,E(ks1,M)))".This form of Triple-DES is used by the RSAREF library.
DESpcbcencrypt() encrypt/decrypts using the propagating cipher block chaining mode used by Kerberos v4. Its parameters are the same as DESncbcencrypt(). DEScfbencrypt() encrypt/decrypts using cipher feedback mode. This method takes an array of characters as input and outputs and array of characters. It does not require any padding to 8 character groups. Note: the ivec variable is changed and the new changed value needs to be passed to the next call to this function. Since this function runs a complete DES ECB encryption per numbits, this function is only suggested for use when sending small numbers of characters. DEScfb64encrypt() implements CFB mode of DES with 64bit feedback. Why is this useful you ask? Because this routine will allow you to encrypt an arbitrary number of bytes, no 8 byte padding. Each call to this routine will encrypt the input bytes to output and then update ivec and num. num contains 'how far' we are though ivec. If this doesnot make much sense, read more about cfb mode of DES :-).
DESede3cfb64encrypt() and DESede2cfb64encrypt() is the same asDEScfb64encrypt() except that Triple-DES is used.
DESofbencrypt() encrypts using output feedback mode. This method takes an array of characters as input and outputs and array of characters. It does not require any padding to 8 character groups. Note: the ivec variable is changed and the new changed value needs to be passed to the next call to this function. Since this function runs a complete DES ECB encryption per numbits, this function is only suggested for use when sending small numbers of characters. DESofb64encrypt() is the same as DEScfb64encrypt() using Output Feed Back mode. DESede3ofb64encrypt() and DESede2ofb64encrypt() is the same asDESofb64encrypt(), using Triple-DES.
The following functions are included in the DES library for compatibility with the MIT Kerberos library. DEScbccksum() produces an 8 byte checksum based on the input stream (via CBC encryption). The last 4 bytes of the checksum are returned and the complete 8 bytes are placed in output. This function is used by Kerberos v4. Other applications should use EVPDigestInit(3) etc. instead. DESquadcksum() is a Kerberos v4 function. It returns a 4 byte checksum from the input bytes. The algorithm can be iterated over theinput, depending on outcount, 1, 2, 3 or 4 times. If output is non-
NULL, the 8 bytes generated by each pass are written into output.The following are DES-based transformations:
DESfcrypt() is a fast version of the Unix crypt(3) function. This version takes only a small amount of space relative to other fast crypt() implementations. This is different to the normal crypt in that the third parameter is the buffer that the return value is written into. It needs to be at least 14 bytes long. This function is thread safe, unlike the normal crypt. DEScrypt() is a faster replacement for the normal system crypt(). This function calls DESfcrypt() with a static array passed as thethird parameter. This emulates the normal non-thread safe semantics of
crypt(3). DESencwrite() writes len bytes to file descriptor fd from buffer buf. The data is encrypted via pcbcencrypt (default) using sched for the key and iv as a starting vector. The actual data send down fd consists of 4 bytes (in network byte order) containing the length of the following encrypted data. The encrypted data then follows, padded with random data out to a multiple of 8 bytes. DESencread() is used to read len bytes from file descriptor fd into buffer buf. The data being read from fd is assumed to have come from DESencwrite() and is decrypted using sched for the key schedule and iv for the initial vector. WWaarrnniinngg:: The data format used by DESencwrite() and DESencread() has a cryptographic weakness: When asked to write more than MAXWRITE bytes, DESencwrite() will split the data into several chunks that are all encrypted using the same IV. So don't use these functions unless you are sure you know what you do (in which case you might not want to usethem anyway). They cannot handle non-blocking sockets. DESencread()
uses an internal state and thus cannot be used on multiple files. DESrwmode is used to specify the encryption mode to use with DESencread() and DESendwrite(). If set to DESPCBCMODE (the default), DESpcbcencrypt is used. If set to DESCBCMODE DEScbcencrypt is used. NNOOTTEESSSingle-key DES is insecure due to its short key size. ECB mode is not
suitable for most applications; see desmodes(7).The evp(3) library provides higher-level encryption functions.
BUGS
DES3cbcencrypt() is flawed and must not be used in applications. DEScbcencrypt() does not modify iivveecc; use DESncbcencrypt() instead. DEScfbencrypt() and DESofbencrypt() operates on input of 8 bits. What this means is that if you set numbits to 12, and length to 2, the first 12 bits will come from the 1st input byte and the low half of the second input byte. The second 12 bits will have the low 8 bits taken from the 3rd input byte and the top 4 bits taken from the 4th input byte. The same holds for output. This function has been implemented this way because most people will be using a multiple of 8 and because once you get into pulling bytes input bytes apart things get ugly! DESstringtokey() is available for backward compatibility with the MIT library. New applications should use a cryptographic hash function. The same applies for DESstringto2key(). CCOONNFFOORRMMIINNGG TTOO ANSI X3.106 The ddeess library was written to be source code compatible with the MIT Kerberos library.SEE ALSO
crypt(3), desmodes(7), evp(3), rand(3) HISTORY In OpenSSL 0.9.7, all des functions were renamed to DES to avoid clashes with older versions of libdes. Compatibility des functions are provided for a short while, as well as crypt(). Declarations for these are in. There is no DES variant for desrandomseed(). This will happen to other functions as well if they are deemed redundant (desrandomseed() just calls RANDseed() and is present for backward compatibility only), buggy or already scheduled for removal. descbccksum(), descbcencrypt(), desecbencrypt(), desisweakkey(), deskeysched(), despcbcencrypt(), desquadcksum(), desrandomkey() and desstringtokey() are available in the MIT Kerberos library; descheckkeyparity(), desfixupkeyparity() and desisweakkey() are available in newer versions of that library. dessetkeychecked() and dessetkeyunchecked() were added in OpenSSL 0.9.5. desgeneraterandomblock(), desinitrandomnumbergenerator(), desnewrandomkey(), dessetrandomgeneratorseed() and dessetsequencenumber() and desranddata() are used in newer versions of Kerberos but are not implemented here. desrandomkey() generated cryptographically weak random data in SSLeay and in OpenSSL prior version 0.9.5, as well as in the original MIT library. AUTHOR Eric Young (eay@cryptsoft.com). Modified for the OpenSSL project (http://www.openssl.org). 0.9.7l 2003-10-01 des(3)