510 lines
13 KiB
Groff
510 lines
13 KiB
Groff
.\" $FreeBSD$
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.TH DES_CRYPT 3
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.SH NAME
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des_read_password, des_read_2password,
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des_string_to_key, des_string_to_2key, des_read_pw_string,
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des_random_key, des_set_key,
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des_key_sched, des_ecb_encrypt, des_ecb3_encrypt, des_cbc_encrypt,
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des_3cbc_encrypt,
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des_pcbc_encrypt, des_cfb_encrypt, des_ofb_encrypt,
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des_cbc_cksum, des_quad_cksum,
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des_enc_read, des_enc_write, des_set_odd_parity,
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des_is_weak_key, crypt \- (non USA) DES encryption
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.SH SYNOPSIS
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.nf
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.nj
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.ft B
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#include <openssl/des.h>
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.PP
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.B int des_read_password(key,prompt,verify)
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des_cblock *key;
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char *prompt;
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int verify;
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.PP
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.B int des_read_2password(key1,key2,prompt,verify)
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des_cblock *key1,*key2;
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char *prompt;
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int verify;
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.PP
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.B int des_string_to_key(str,key)
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char *str;
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des_cblock *key;
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.PP
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.B int des_string_to_2keys(str,key1,key2)
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char *str;
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des_cblock *key1,*key2;
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.PP
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.B int des_read_pw_string(buf,length,prompt,verify)
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char *buf;
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int length;
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char *prompt;
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int verify;
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.PP
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.B int des_random_key(key)
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des_cblock *key;
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.PP
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.B int des_set_key(key,schedule)
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des_cblock *key;
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des_key_schedule schedule;
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.PP
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.B int des_key_sched(key,schedule)
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des_cblock *key;
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des_key_schedule schedule;
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.PP
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.B int des_ecb_encrypt(input,output,schedule,encrypt)
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des_cblock *input;
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des_cblock *output;
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des_key_schedule schedule;
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int encrypt;
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.PP
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.B int des_ecb3_encrypt(input,output,ks1,ks2,encrypt)
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des_cblock *input;
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des_cblock *output;
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des_key_schedule ks1,ks2;
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int encrypt;
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.PP
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.B int des_cbc_encrypt(input,output,length,schedule,ivec,encrypt)
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des_cblock *input;
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des_cblock *output;
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long length;
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des_key_schedule schedule;
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des_cblock *ivec;
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int encrypt;
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.PP
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.B int des_3cbc_encrypt(input,output,length,sk1,sk2,ivec1,ivec2,encrypt)
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des_cblock *input;
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des_cblock *output;
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long length;
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des_key_schedule sk1;
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des_key_schedule sk2;
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des_cblock *ivec1;
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des_cblock *ivec2;
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int encrypt;
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.PP
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.B int des_pcbc_encrypt(input,output,length,schedule,ivec,encrypt)
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des_cblock *input;
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des_cblock *output;
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long length;
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des_key_schedule schedule;
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des_cblock *ivec;
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int encrypt;
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.PP
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.B int des_cfb_encrypt(input,output,numbits,length,schedule,ivec,encrypt)
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unsigned char *input;
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unsigned char *output;
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int numbits;
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long length;
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des_key_schedule schedule;
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des_cblock *ivec;
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int encrypt;
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.PP
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.B int des_ofb_encrypt(input,output,numbits,length,schedule,ivec)
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unsigned char *input,*output;
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int numbits;
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long length;
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des_key_schedule schedule;
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des_cblock *ivec;
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.PP
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.B unsigned long des_cbc_cksum(input,output,length,schedule,ivec)
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des_cblock *input;
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des_cblock *output;
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long length;
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des_key_schedule schedule;
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des_cblock *ivec;
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.PP
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.B unsigned long des_quad_cksum(input,output,length,out_count,seed)
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des_cblock *input;
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des_cblock *output;
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long length;
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int out_count;
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des_cblock *seed;
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.PP
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.B int des_check_key;
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.PP
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.B int des_enc_read(fd,buf,len,sched,iv)
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int fd;
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char *buf;
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int len;
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des_key_schedule sched;
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des_cblock *iv;
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.PP
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.B int des_enc_write(fd,buf,len,sched,iv)
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int fd;
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char *buf;
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int len;
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des_key_schedule sched;
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des_cblock *iv;
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.PP
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.B extern int des_rw_mode;
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.PP
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.B void des_set_odd_parity(key)
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des_cblock *key;
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.PP
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.B int des_is_weak_key(key)
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des_cblock *key;
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.PP
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.B char *crypt(passwd,salt)
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char *passwd;
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char *salt;
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.PP
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.fi
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.SH DESCRIPTION
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This library contains a fast implementation of the DES encryption
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algorithm.
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.PP
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There are two phases to the use of DES encryption.
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The first is the generation of a
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.I des_key_schedule
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from a key,
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the second is the actual encryption.
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A des key is of type
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.I des_cblock.
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This type is made from 8 characters with odd parity.
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The least significant bit in the character is the parity bit.
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The key schedule is an expanded form of the key; it is used to speed the
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encryption process.
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.PP
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.I des_read_password
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writes the string specified by prompt to the standard output,
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turns off echo and reads an input string from standard input
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until terminated with a newline.
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If verify is non-zero, it prompts and reads the input again and verifies
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that both entered passwords are the same.
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The entered string is converted into a des key by using the
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.I des_string_to_key
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routine.
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The new key is placed in the
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.I des_cblock
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that was passed (by reference) to the routine.
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If there were no errors,
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.I des_read_password
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returns 0,
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-1 is returned if there was a terminal error and 1 is returned for
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any other error.
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.PP
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.I des_read_2password
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operates in the same way as
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.I des_read_password
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except that it generates 2 keys by using the
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.I des_string_to_2key
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function.
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.PP
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.I des_read_pw_string
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is called by
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.I des_read_password
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to read and verify a string from a terminal device.
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The string is returned in
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.I buf.
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The size of
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.I buf
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is passed to the routine via the
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.I length
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parameter.
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.PP
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.I des_string_to_key
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converts a string into a valid des key.
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.PP
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.I des_string_to_2key
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converts a string into 2 valid des keys.
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This routine is best suited for used to generate keys for use with
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.I des_ecb3_encrypt.
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.PP
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.I des_random_key
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returns a random key that is made of a combination of process id,
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time and an increasing counter.
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.PP
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Before a des key can be used it is converted into a
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.I des_key_schedule
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via the
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.I des_set_key
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routine.
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If the
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.I des_check_key
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flag is non-zero,
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.I des_set_key
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will check that the key passed is of odd parity and is not a week or
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semi-weak key.
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If the parity is wrong,
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then -1 is returned.
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If the key is a weak key,
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then -2 is returned.
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If an error is returned,
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the key schedule is not generated.
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.PP
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.I des_key_sched
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is another name for the
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.I des_set_key
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function.
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.PP
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The following routines mostly operate on an input and output stream of
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.I des_cblock's.
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.PP
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.I des_ecb_encrypt
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is the basic DES encryption routine that encrypts or decrypts a single 8-byte
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.I des_cblock
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in
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.I electronic code book
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mode.
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It always transforms the input data, pointed to by
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.I input,
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into the output data,
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pointed to by the
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.I output
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argument.
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If the
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.I encrypt
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argument is non-zero (DES_ENCRYPT),
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the
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.I input
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(cleartext) is encrypted in to the
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.I output
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(ciphertext) using the key_schedule specified by the
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.I schedule
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argument,
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previously set via
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.I des_set_key.
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If
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.I encrypt
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is zero (DES_DECRYPT),
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the
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.I input
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(now ciphertext)
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is decrypted into the
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.I output
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(now cleartext).
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Input and output may overlap.
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No meaningful value is returned.
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.PP
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.I des_ecb3_encrypt
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encrypts/decrypts the
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.I input
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block by using triple ecb DES encryption.
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This involves encrypting the input with
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.I ks1,
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decryption with the key schedule
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.I ks2,
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and then encryption with the first again.
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This routine greatly reduces the chances of brute force breaking of
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DES and has the advantage of if
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.I ks1
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and
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.I ks2
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are the same, it is equivalent to just encryption using ecb mode and
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.I ks1
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as the key.
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.PP
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.I des_cbc_encrypt
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encrypts/decrypts using the
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.I cipher-block-chaining
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mode of DES.
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If the
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.I encrypt
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argument is non-zero,
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the routine cipher-block-chain encrypts the cleartext data pointed to by the
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.I input
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argument into the ciphertext pointed to by the
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.I output
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argument,
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using the key schedule provided by the
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.I schedule
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argument,
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and initialisation vector provided by the
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.I ivec
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argument.
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If the
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.I length
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argument is not an integral multiple of eight bytes,
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the last block is copied to a temporary area and zero filled.
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The output is always
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an integral multiple of eight bytes.
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To make multiple cbc encrypt calls on a large amount of data appear to
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be one
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.I des_cbc_encrypt
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call, the
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.I ivec
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of subsequent calls should be the last 8 bytes of the output.
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.PP
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.I des_3cbc_encrypt
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encrypts/decrypts the
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.I input
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block by using triple cbc DES encryption.
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This involves encrypting the input with key schedule
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.I ks1,
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decryption with the key schedule
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.I ks2,
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and then encryption with the first again.
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2 initialisation vectors are required,
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.I ivec1
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and
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.I ivec2.
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Unlike
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.I des_cbc_encrypt,
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these initialisation vectors are modified by the subroutine.
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This routine greatly reduces the chances of brute force breaking of
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DES and has the advantage of if
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.I ks1
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and
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.I ks2
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are the same, it is equivalent to just encryption using cbc mode and
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.I ks1
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as the key.
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.PP
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.I des_pcbc_encrypt
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encrypt/decrypts using a modified block chaining mode.
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It provides better error propagation characteristics than cbc
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encryption.
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.PP
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.I des_cfb_encrypt
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encrypt/decrypts using cipher feedback mode. This method takes an
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array of characters as input and outputs and array of characters. It
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does not require any padding to 8 character groups. Note: the ivec
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variable is changed and the new changed value needs to be passed to
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the next call to this function. Since this function runs a complete
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DES ecb encryption per numbits, this function is only suggested for
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use when sending small numbers of characters.
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.PP
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.I des_ofb_encrypt
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encrypt using output feedback mode. This method takes an
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array of characters as input and outputs and array of characters. It
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does not require any padding to 8 character groups. Note: the ivec
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variable is changed and the new changed value needs to be passed to
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the next call to this function. Since this function runs a complete
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DES ecb encryption per numbits, this function is only suggested for
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use when sending small numbers of characters.
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.PP
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.I des_cbc_cksum
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produces an 8 byte checksum based on the input stream (via cbc encryption).
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The last 4 bytes of the checksum is returned and the complete 8 bytes is
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placed in
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.I output.
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.PP
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.I des_quad_cksum
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returns a 4 byte checksum from the input bytes.
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The algorithm can be iterated over the input,
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depending on
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.I out_count,
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1, 2, 3 or 4 times.
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If
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.I output
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is non-NULL,
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the 8 bytes generated by each pass are written into
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.I output.
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.PP
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.I des_enc_write
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is used to write
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.I len
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bytes
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to file descriptor
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.I fd
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from buffer
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.I buf.
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The data is encrypted via
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.I pcbc_encrypt
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(default) using
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.I sched
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for the key and
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.I iv
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as a starting vector.
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The actual data send down
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.I fd
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consists of 4 bytes (in network byte order) containing the length of the
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following encrypted data. The encrypted data then follows, padded with random
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data out to a multiple of 8 bytes.
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.PP
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.I des_enc_read
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is used to read
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.I len
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bytes
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from file descriptor
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.I fd
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into buffer
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.I buf.
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The data being read from
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.I fd
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is assumed to have come from
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.I des_enc_write
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and is decrypted using
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.I sched
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for the key schedule and
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.I iv
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for the initial vector.
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The
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.I des_enc_read/des_enc_write
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pair can be used to read/write to files, pipes and sockets.
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I have used them in implementing a version of rlogin in which all
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data is encrypted.
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.PP
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.I des_rw_mode
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is used to specify the encryption mode to use with
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.I des_enc_read
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and
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.I des_end_write.
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If set to
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.I DES_PCBC_MODE
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(the default), des_pcbc_encrypt is used.
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If set to
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.I DES_CBC_MODE
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des_cbc_encrypt is used.
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These two routines and the variable are not part of the normal MIT library.
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.PP
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.I des_set_odd_parity
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sets the parity of the passed
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.I key
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to odd. This routine is not part of the standard MIT library.
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.PP
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.I des_is_weak_key
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returns 1 is the passed key is a weak key (pick again :-),
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0 if it is ok.
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This routine is not part of the standard MIT library.
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.PP
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.I crypt
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is a replacement for the normal system crypt.
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It is much faster than the system crypt.
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.PP
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.SH FILES
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/usr/include/openssl/des.h
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.br
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/usr/lib/libcrypto.a
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.PP
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The encryption routines have been tested on 16bit, 32bit and 64bit
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machines of various endian and even works under VMS.
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.PP
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.SH BUGS
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.PP
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If you think this manual is sparse,
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read the des_crypt(3) manual from the MIT kerberos (or bones outside
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of the USA) distribution.
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.PP
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.I des_cfb_encrypt
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and
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.I des_ofb_encrypt
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operates on input of 8 bits. What this means is that if you set
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numbits to 12, and length to 2, the first 12 bits will come from the 1st
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input byte and the low half of the second input byte. The second 12
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bits will have the low 8 bits taken from the 3rd input byte and the
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top 4 bits taken from the 4th input byte. The same holds for output.
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This function has been implemented this way because most people will
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be using a multiple of 8 and because once you get into pulling bytes input
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bytes apart things get ugly!
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.PP
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.I des_read_pw_string
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is the most machine/OS dependent function and normally generates the
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most problems when porting this code.
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.PP
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.I des_string_to_key
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is probably different from the MIT version since there are lots
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of fun ways to implement one-way encryption of a text string.
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.PP
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The routines are optimised for 32 bit machines and so are not efficient
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on IBM PCs.
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.PP
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NOTE: extensive work has been done on this library since this document
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was origionally written. Please try to read des.doc from the libdes
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distribution since it is far more upto date and documents more of the
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functions. Libdes is now also being shipped as part of SSLeay, a
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general cryptographic library that amonst other things implements
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netscapes SSL protocoll. The most recent version can be found in
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SSLeay distributions.
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.SH AUTHOR
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Eric Young (eay@cryptsoft.com)
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