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Diffstat (limited to 'man/man3/des.3')
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diff --git a/man/man3/des.3 b/man/man3/des.3 new file mode 100644 index 00000000..c99fd578 --- /dev/null +++ b/man/man3/des.3 @@ -0,0 +1,144 @@ +.TH DES 3 +.SH NAME +setupDESstate, des_key_setup, block_cipher, desCBCencrypt, desCBCdecrypt, desECBencrypt, desECBdecrypt, des3CBCencrypt, des3CBCdecrypt, des3ECBencrypt, des3ECBdecrypt, key_setup, des56to64, des64to56, setupDES3state, triple_block_cipher, - single and triple digital encryption standard +.SH SYNOPSIS +.B #include <u.h> +.br +.B #include <libc.h> +.br +.B #include <mp.h> +.br +.B #include <libsec.h> +.PP +.B +void des_key_setup(uchar key[8], ulong schedule[32]) +.PP +.B +void block_cipher(ulong *schedule, uchar *data, +.B + int decrypting) +.PP +.B +void setupDESstate(DESstate *s, uchar key[8], uchar *ivec) +.PP +.B +void desCBCencrypt(uchar*, int, DESstate*) +.PP +.B +void desCBCdecrypt(uchar*, int, DESstate*) +.PP +.B +void desECBencrypt(uchar*, int, DESstate*) +.PP +.B +void desECBdecrypt(uchar*, int, DESstate*) +.PP +.B +void triple_block_cipher(ulong keys[3][32], uchar*, int) +.PP +.B +void setupDES3state(DES3state *s, uchar key[3][8], +.B + uchar *ivec) +.PP +.B +void des3CBCencrypt(uchar*, int, DES3state*) +.PP +.B +void des3CBCdecrypt(uchar*, int, DES3state*) +.PP +.B +void des3ECBencrypt(uchar*, int, DES3state*) +.PP +.B +void des3ECBdecrypt(uchar*, int, DES3state*) +.PP +.B +void key_setup(uchar[7], ulong[32]) +.PP +.B +void des56to64(uchar *k56, uchar *k64) +.PP +.B +void des64to56(uchar *k64, uchar *k56) +.SH DESCRIPTION +.PP +The Digital Encryption Standard (DES) +is a shared key or symmetric encryption using either +a 56 bit key for single DES or three 56 bit keys for triple des. +The keys are encoded into 64 bits where every eight bit +is parity. +.PP +The basic DES function, +.IR block_cipher , +works on a block of 8 bytes, converting them in place. +It takes a key schedule, a pointer to the block, and +a flag indicating encrypting (0) or decrypting (1). +The key schedule is created from the key using +.IR des_key_setup . +.PP +Since it is a bit awkward, +.I block_cipher +is rarely called directly. Instead, one normally uses +routines that encrypt larger buffers of data and +which may chain the encryption state from one buffer +to the next. +These routines keep track of the state of the +encryption using a +.B DESstate +structure that contains the key schedule and any chained +state. +.I SetupDESstate +sets up the +.B DESstate +structure using the key and an 8 byte initialization vector. +.PP +Electronic code book, using +.I desECBencrypt +and +.IR desECBdecrypt , +is the less secure mode. The encryption of each 8 bytes +does not depend on the encryption of any other. +Hence the encryption is a substitution +cipher using 64 bit characters. +.PP +Cipher block chaining mode, using +.I desCBCencrypt +and +.IR desCBCdecrypt , +is more secure. Every block encrypted depends on the initialization +vector and all blocks encrypted before it. +.PP +For both CBC and ECB modes, a stream of data can be encrypted as +multiple buffers. However, all buffers except the last must +be a multiple of 8 bytes to ensure successful decryption of +the stream. +.PP +There are equivalent triple DES functions for each of the +DES functions. +.PP +In the past Plan 9 used a 56 bit or 7 byte +format for DES keys. To be compatible with the rest +of the world, we've abandoned this format. +There are two functions: +.I des56to64 +and +.I des64to56 +to convert back and forth between the two formats. +Also a key schedule can be set up from the 7 byte format +using +.IR key_setup . +.PP +.SH SOURCE +.B /sys/src/libsec +.SH SEE ALSO +.IR mp (2), +.IR aes (2), +.IR blowfish (2), +.IR dsa (2), +.IR elgamal (2), +.IR rc4 (2), +.IR rsa (2), +.IR sechash (2), +.IR prime (2), +.IR rand (2) |