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*Manual Reference Pages - *des (3SSL)

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### SYNOPSIS

### DESCRIPTION

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DES_random_key, DES_set_key, DES_key_sched, DES_set_key_checked, DES_set_key_unchecked, DES_set_odd_parity, DES_is_weak_key, DES_ecb_encrypt, DES_ecb2_encrypt, DES_ecb3_encrypt, DES_ncbc_encrypt, DES_cfb_encrypt, DES_ofb_encrypt, DES_pcbc_encrypt, DES_cfb64_encrypt, DES_ofb64_encrypt, DES_xcbc_encrypt, DES_ede2_cbc_encrypt, DES_ede2_cfb64_encrypt, DES_ede2_ofb64_encrypt, DES_ede3_cbc_encrypt, DES_ede3_cbcm_encrypt, DES_ede3_cfb64_encrypt, DES_ede3_ofb64_encrypt, DES_cbc_cksum, DES_quad_cksum, DES_string_to_key, DES_string_to_2keys, DES_fcrypt, DES_crypt, DES_enc_read, DES_enc_write - DES encryption

#include <openssl/des.h> void DES_random_key(DES_cblock *ret); int DES_set_key(const_DES_cblock *key, DES_key_schedule *schedule); int DES_key_sched(const_DES_cblock *key, DES_key_schedule *schedule); int DES_set_key_checked(const_DES_cblock *key, DES_key_schedule *schedule); void DES_set_key_unchecked(const_DES_cblock *key, DES_key_schedule *schedule); void DES_set_odd_parity(DES_cblock *key); int DES_is_weak_key(const_DES_cblock *key); void DES_ecb_encrypt(const_DES_cblock *input, DES_cblock *output, DES_key_schedule *ks, int enc); void DES_ecb2_encrypt(const_DES_cblock *input, DES_cblock *output, DES_key_schedule *ks1, DES_key_schedule *ks2, int enc); void DES_ecb3_encrypt(const_DES_cblock *input, DES_cblock *output, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_key_schedule *ks3, int enc); void DES_ncbc_encrypt(const unsigned char *input, unsigned char *output, long length, DES_key_schedule *schedule, DES_cblock *ivec, int enc); void DES_cfb_encrypt(const unsigned char *in, unsigned char *out, int numbits, long length, DES_key_schedule *schedule, DES_cblock *ivec, int enc); void DES_ofb_encrypt(const unsigned char *in, unsigned char *out, int numbits, long length, DES_key_schedule *schedule, DES_cblock *ivec); void DES_pcbc_encrypt(const unsigned char *input, unsigned char *output, long length, DES_key_schedule *schedule, DES_cblock *ivec, int enc); void DES_cfb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *schedule, DES_cblock *ivec, int *num, int enc); void DES_ofb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *schedule, DES_cblock *ivec, int *num); void DES_xcbc_encrypt(const unsigned char *input, unsigned char *output, long length, DES_key_schedule *schedule, DES_cblock *ivec, const_DES_cblock *inw, const_DES_cblock *outw, int enc); void DES_ede2_cbc_encrypt(const unsigned char *input, unsigned char *output, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int enc); void DES_ede2_cfb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num, int enc); void DES_ede2_ofb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num); void DES_ede3_cbc_encrypt(const unsigned char *input, unsigned char *output, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_key_schedule *ks3, DES_cblock *ivec, int enc); void DES_ede3_cbcm_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_key_schedule *ks3, DES_cblock *ivec1, DES_cblock *ivec2, int enc); void DES_ede3_cfb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_key_schedule *ks3, DES_cblock *ivec, int *num, int enc); void DES_ede3_ofb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_key_schedule *ks3, DES_cblock *ivec, int *num); DES_LONG DES_cbc_cksum(const unsigned char *input, DES_cblock *output, long length, DES_key_schedule *schedule, const_DES_cblock *ivec); DES_LONG DES_quad_cksum(const unsigned char *input, DES_cblock output[], long length, int out_count, DES_cblock *seed); void DES_string_to_key(const char *str, DES_cblock *key); void DES_string_to_2keys(const char *str, DES_cblock *key1, DES_cblock *key2); char *DES_fcrypt(const char *buf, const char *salt, char *ret); char *DES_crypt(const char *buf, const char *salt); int DES_enc_read(int fd, void *buf, int len, DES_key_schedule *sched, DES_cblock *iv); int DES_enc_write(int fd, const void *buf, int len, DES_key_schedule *sched, DES_cblock *iv);

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

DES_key_schedulefrom a key, the second is the actual encryption. A DES key is of typeDES_cblock. 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.

DES_random_key()generates a random key. The PRNG must be seeded prior to using this function (seerand(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

DES_key_schedulevia theDES_set_key_checked()orDES_set_key_unchecked()function.

DES_set_key_checked()will check that the key passed is of odd parity and 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.

DES_set_key()works likeDES_set_key_checked()if theDES_check_keyflag is non-zero, otherwise likeDES_set_key_unchecked(). These functions are available for compatibility; it is recommended to use a function that does not depend on a global variable.

DES_set_odd_parity()sets the parity of the passedkeyto odd.

DES_is_weak_key()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

DES_cblocks.

DES_ecb_encrypt()is the basic DES encryption routine that encrypts or decrypts a single 8-byteDES_cblockinelectronic code book(ECB) mode. It always transforms the input data, pointed to byinput, into the output data, pointed to by theoutputargument. If theencryptargument is non-zero (DES_ENCRYPT), theinput(cleartext) is encrypted in to theoutput(ciphertext) using the key_schedule specified by thescheduleargument, previously set viaDES_set_key. Ifencryptis zero (DES_DECRYPT), theinput(now ciphertext) is decrypted into theoutput(now cleartext). Input and output may overlap.DES_ecb_encrypt()does not return a value.

DES_ecb3_encrypt()encrypts/decrypts theinputblock by using three-key Triple-DES encryption in ECB mode. This involves encrypting the input withks1, decrypting with the key scheduleks2, and then encrypting withks3. This routine greatly reduces the chances of brute force breaking of DES and has the advantage of ifks1,ks2andks3are the same, it is equivalent to just encryption using ECB mode andks1as the key.The macro

DES_ecb2_encrypt()is provided to perform two-key Triple-DES encryption by usingks1for the final encryption.

DES_ncbc_encrypt()encrypts/decrypts using thecipher-block-chaining(CBC) mode of DES. If theencryptargument is non-zero, the routine cipher-block-chain encrypts the cleartext data pointed to by theinputargument into the ciphertext pointed to by theoutputargument, using the key schedule provided by thescheduleargument, and initialization vector provided by theivecargument. If thelengthargument 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.

DES_xcbc_encrypt()is RSA’s DESX mode of DES. It usesinwandoutwto ’whiten’ the encryption.inwandoutware 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.

DES_ede3_cbc_encrypt()implements outer triple CBC DES encryption with three keys. This means that each DES operation inside the CBC mode is really anC=E(ks3,D(ks2,E(ks1,M))). This mode is used by SSL.The

DES_ede2_cbc_encrypt()macro implements two-key Triple-DES by reusingks1for the final encryption.C=E(ks1,D(ks2,E(ks1,M))). This form of Triple-DES is used by the RSAREF library.

DES_pcbc_encrypt()encrypt/decrypts using the propagating cipher block chaining mode used by Kerberos v4. Its parameters are the same asDES_ncbc_encrypt().

DES_cfb_encrypt()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: theivecvariable 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 pernumbits, this function is only suggested for use when sending small numbers of characters.

DES_cfb64_encrypt()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 does not make much sense, read more about cfb mode of DES :-).

DES_ede3_cfb64_encrypt()andDES_ede2_cfb64_encrypt()is the same asDES_cfb64_encrypt()except that Triple-DES is used.

DES_ofb_encrypt()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: theivecvariable 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.

DES_ofb64_encrypt()is the same asDES_cfb64_encrypt()using Output Feed Back mode.

DES_ede3_ofb64_encrypt()andDES_ede2_ofb64_encrypt()is the same asDES_ofb64_encrypt(), using Triple-DES.The following functions are included in the DES library for compatibility with the MIT Kerberos library.

DES_cbc_cksum()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 inoutput. This function is used by Kerberos v4. Other applications should useEVP_DigestInit(3) etc. instead.

DES_quad_cksum()is a Kerberos v4 function. It returns a 4 byte checksum from the input bytes. The algorithm can be iterated over the input, depending onout_count, 1, 2, 3 or 4 times. Ifoutputis non-NULL, the 8 bytes generated by each pass are written intooutput.The following are DES-based transformations:

DES_fcrypt()is a fast version of the Unixcrypt(3) function. This version takes only a small amount of space relative to other fastcrypt()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.

DES_crypt()is a faster replacement for the normal systemcrypt(). This function callsDES_fcrypt()with a static array passed as the third parameter. This emulates the normal non-thread safe semantics ofcrypt(3).

DES_enc_write()writeslenbytes to file descriptorfdfrom bufferbuf. The data is encrypted viapcbc_encrypt(default) usingschedfor the key andivas a starting vector. The actual data send downfdconsists 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.

DES_enc_read()is used to readlenbytes from file descriptorfdinto bufferbuf. The data being read fromfdis assumed to have come fromDES_enc_write()and is decrypted usingschedfor the key schedule andivfor the initial vector.

Warning:The data format used byDES_enc_write()andDES_enc_read()has a cryptographic weakness: When asked to write more than MAXWRITE bytes,DES_enc_write()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 use them anyway). They cannot handle non-blocking sockets.DES_enc_read()uses an internal state and thus cannot be used on multiple files.

DES_rw_modeis used to specify the encryption mode to use withDES_enc_read()andDES_end_write(). If set toDES_PCBC_MODE(the default), DES_pcbc_encrypt is used. If set toDES_CBC_MODEDES_cbc_encrypt is used.

Single-key DES is insecure due to its short key size. ECB mode is not suitable for most applications; seedes_modes(7).The

evp(3) library provides higher-level encryption functions.

DES_3cbc_encrypt()is flawed and must not be used in applications.

DES_cbc_encrypt()does not modifyivec; useDES_ncbc_encrypt()instead.

DES_cfb_encrypt()andDES_ofb_encrypt()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!

DES_string_to_key()is available for backward compatibility with the MIT library. New applications should use a cryptographic hash function. The same applies forDES_string_to_2key().

ANSI X3.106The

deslibrary was written to be source code compatible with the MIT Kerberos library.

crypt(3),des_modes(7),evp(3),rand(3)

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 ascrypt(). Declarations for these are in <openssl/des_old.h>. There is no DES_ variant fordes_random_seed(). This will happen to other functions as well if they are deemed redundant (des_random_seed()just callsRAND_seed()and is present for backward compatibility only), buggy or already scheduled for removal.

des_cbc_cksum(),des_cbc_encrypt(),des_ecb_encrypt(),des_is_weak_key(),des_key_sched(),des_pcbc_encrypt(),des_quad_cksum(),des_random_key()anddes_string_to_key()are available in the MIT Kerberos library;des_check_key_parity(),des_fixup_key_parity()anddes_is_weak_key()are available in newer versions of that library.

des_set_key_checked()anddes_set_key_unchecked()were added in OpenSSL 0.9.5.

des_generate_random_block(),des_init_random_number_generator(),des_new_random_key(),des_set_random_generator_seed()anddes_set_sequence_number()anddes_rand_data()are used in newer versions of Kerberos but are not implemented here.

des_random_key()generated cryptographically weak random data in SSLeay and in OpenSSL prior version 0.9.5, as well as in the original MIT library.

Eric Young (eay@cryptsoft.com). Modified for the OpenSSL project (http://www.openssl.org).

1.0.1e |
des (3SSL) | 2013-02-11 |