A Convention for Human-Readable 128-bit Keys
draft-mcdonald-readable-keys-00
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This is an older version of an Internet-Draft that was ultimately published as RFC 1751.
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Author | Daniel L. McDonald | ||
Last updated | 2020-01-21 (Latest revision 1994-08-16) | ||
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draft-mcdonald-readable-keys-00
Network Working Group D. McDonald INTERNET-DRAFT NRL draft-mcdonald-readable-keys-00.txt 20 August 1994 A Convention for Human-Readable 128-bit Keys Status of this Memo Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. This Internet Draft expires on February 20, 1995. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress." Please check the I-D abstract listing contained in each Internet Draft directory to learn the current status of this or any other Internet Draft. Distribution of this memo is unlimited. Introduction The Internet community has begun to address matters of security. Recent standards, including version 2 of SNMP [GM93], and version 6 of IP [Atk94] have explicit requirements for an authentication mechanism. Both require used of a keyed message-digest algorithm, MD5 [Riv92]. Both require a key size of 128-bits. A 128-bit key, while sufficiently strong, is hard for most people to read, remember, and type in. A Solution Already Exists The S/Key(tm) one-time password system [Hal94] uses MD4 (and now MD5, as well) to compute one-time passwords. It takes the 128-bit result of MD4 and collapses it to a 64-bit result. Despite the size reduction, 64-bit one-time passwords are still difficult for ordinary people to remember and enter. The authors of S/Key devised a system to make the 64-bit one-time password easy for people to enter. Their idea was to transform the password into a string of small English words. English words are significantly easier for people to McDonald [Page 1] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 both remember and type. The authors of S/Key started with a dictionary of 2048 English words, ranging in length from one to four characters. The space covered by a 64-bit key (2^64) could be covered by six words from this dictionary (2^66) with room remaining for parity. For example, an S/Key one-time password of hex value: EB33 F77E E73D 4053 would become the following six English words: TIDE ITCH SLOW REIN RULE MOT The Proposal The code (see Appendix A) which S/Key uses to convert 64-bit numbers to six English words contains two primitives which perform conversions either way. The primitive btoe(char *engout,char *c) takes a 64-bit quantity referenced by c and places English words in the string referenced by engout. The primitive etob(char *out,char *e) performs the opposite with an input string of English words referenced by e, and by placing the 64-bit result into the buffer referenced by out. The aforementioned primitives can be applied to both halves of a 128-bit key, or both halves of a string of twelve English words. Two new primitives (see Appendix B), key2eng(char *engout,char *key) and eng2key(char *keyout,char *eng) serve as wrappers which call the S/Key primitives twice, once for each half of the 128-bit key or string of twelve words. For example, the 128-bit key of: CCAC 2AED 5910 56BE 4F90 FD44 1C53 4766 would become RASH BUSH MILK LOOK BAD BRIM AVID GAFF BAIT ROT POD LOVE Likewise, a user should be able to type in TROD MUTE TAIL WARM CHAR KONG HAAG CITY BORE O TEAL AWL as a key, and the machine should make the translation to: EFF8 1F9B FBC6 5350 920C DD74 16DE 8009 If this proposal is to work, it is critical that the dictionary of English words does not change with different implementations. A McDonald [Page 2] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 freely redistributable reference implementation is given in Appendices A and B. Security Considerations This document recommends a method of representing 128-bit keys using strings of English words. Since the strings of English words are easy to remember, people may potentially construct easy-to-guess strings of English words. With easy-to-guess strings comes the possibility of a sentential equivalent of a dictionary attack. In order to maximize the strength of any authentication mechanism that uses 128-bit keys, the keys must be sufficiently obscure. In particular, people should avoid the temptation to devise sentences. References [Atk94] Atkinson, Randall, "IPv6 Authentication Header", Internet- Draft, August 1994. [GM93] Galvin, J. and McCloghrie, K., "Security Protocols for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC1446, Internet Architecture Board, April 1993. [Hal94] Haller, Neil M., "The S/Key(tm) One-Time Password System", Proceedings of the Symposium on Network & Distributed Systems Security, Internet Society, San Diego, February 1994. [Riv92] Rivest, R., "The MD5 Message-Digest Algorithm", RFC1321, Internet Architecture Board, April 1992. Author's Address Daniel L. McDonald United States Naval Research Laboratory Code 5544 4555 Overlook Ave. SW Washington, DC 20375 Phone: (202) 404-7122 E-mail: danmcd@itd.nrl.navy.mil McDonald [Page 3] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 Appendix A - Source for S/Key 8-bytes to/from Words Routines (put.c) /* This code originally appeared in the source for S/Key, available in the * directory * ftp://thumper.bellcore.com/pub/nmh * * It has been modified only to remove explicit S/Key references. */ #include <stdio.h> #include <string.h> #include <assert.h> #include <ctype.h> #ifdef __STDC__ #define __ARGS(x) x #else #define __ARGS(x) () #endif static unsigned long extract __ARGS((char *s,int start,int length)); static void standard __ARGS((char *word)); static void insert __ARGS((char *s, int x, int start, int length)); static int wsrch __ARGS((char *w,int low,int high)); /* Dictionary for integer-word translations */ char Wp[2048][4] = { "A", "ABE", "ACE", "ACT", "AD", "ADA", "ADD", "AGO", "AID", "AIM", "AIR", "ALL", "ALP", "AM", "AMY", "AN", "ANA", "AND", "ANN", "ANT", "ANY", "APE", "APS", "APT", "ARC", "ARE", "ARK", "ARM", "ART", "AS", "ASH", "ASK", "AT", "ATE", "AUG", "AUK", "AVE", "AWE", "AWK", "AWL", "AWN", "AX", "AYE", "BAD", "BAG", "BAH", "BAM", "BAN", "BAR", "BAT", "BAY", "BE", "BED", "BEE", "BEG", "BEN", "BET", "BEY", "BIB", "BID", "BIG", "BIN", "BIT", "BOB", "BOG", "BON", "BOO", "BOP", "BOW", "BOY", "BUB", "BUD", "BUG", "BUM", "BUN", "BUS", "BUT", "BUY", "BY", "BYE", "CAB", "CAL", "CAM", "CAN", "CAP", "CAR", "CAT", "CAW", "COD", "COG", "COL", "CON", "COO", "COP", "COT", "COW", "COY", "CRY", "CUB", "CUE", "CUP", "CUR", "CUT", "DAB", "DAD", "DAM", "DAN", "DAR", "DAY", "DEE", "DEL", "DEN", "DES", "DEW", "DID", "DIE", "DIG", "DIN", "DIP", "DO", "DOE", "DOG", "DON", "DOT", "DOW", "DRY", "DUB", "DUD", "DUE", "DUG", "DUN", "EAR", "EAT", "ED", "EEL", "EGG", "EGO", "ELI", "ELK", "ELM", "ELY", "EM", "END", "EST", "ETC", "EVA", "EVE", "EWE", "EYE", "FAD", "FAN", "FAR", "FAT", "FAY", "FED", "FEE", "FEW", "FIB", "FIG", "FIN", "FIR", "FIT", "FLO", "FLY", "FOE", "FOG", "FOR", "FRY", "FUM", "FUN", "FUR", "GAB", "GAD", "GAG", "GAL", "GAM", "GAP", "GAS", "GAY", "GEE", "GEL", "GEM", "GET", "GIG", "GIL", "GIN", "GO", "GOT", "GUM", "GUN", "GUS", "GUT", "GUY", "GYM", "GYP", "HA", "HAD", "HAL", "HAM", "HAN", "HAP", "HAS", "HAT", "HAW", "HAY", "HE", "HEM", "HEN", "HER", "HEW", "HEY", "HI", "HID", "HIM", "HIP", "HIS", "HIT", "HO", "HOB", "HOC", "HOE", "HOG", "HOP", "HOT", "HOW", "HUB", "HUE", "HUG", "HUH", "HUM", "HUT", McDonald [Page 4] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 "I", "ICY", "IDA", "IF", "IKE", "ILL", "INK", "INN", "IO", "ION", "IQ", "IRA", "IRE", "IRK", "IS", "IT", "ITS", "IVY", "JAB", "JAG", "JAM", "JAN", "JAR", "JAW", "JAY", "JET", "JIG", "JIM", "JO", "JOB", "JOE", "JOG", "JOT", "JOY", "JUG", "JUT", "KAY", "KEG", "KEN", "KEY", "KID", "KIM", "KIN", "KIT", "LA", "LAB", "LAC", "LAD", "LAG", "LAM", "LAP", "LAW", "LAY", "LEA", "LED", "LEE", "LEG", "LEN", "LEO", "LET", "LEW", "LID", "LIE", "LIN", "LIP", "LIT", "LO", "LOB", "LOG", "LOP", "LOS", "LOT", "LOU", "LOW", "LOY", "LUG", "LYE", "MA", "MAC", "MAD", "MAE", "MAN", "MAO", "MAP", "MAT", "MAW", "MAY", "ME", "MEG", "MEL", "MEN", "MET", "MEW", "MID", "MIN", "MIT", "MOB", "MOD", "MOE", "MOO", "MOP", "MOS", "MOT", "MOW", "MUD", "MUG", "MUM", "MY", "NAB", "NAG", "NAN", "NAP", "NAT", "NAY", "NE", "NED", "NEE", "NET", "NEW", "NIB", "NIL", "NIP", "NIT", "NO", "NOB", "NOD", "NON", "NOR", "NOT", "NOV", "NOW", "NU", "NUN", "NUT", "O", "OAF", "OAK", "OAR", "OAT", "ODD", "ODE", "OF", "OFF", "OFT", "OH", "OIL", "OK", "OLD", "ON", "ONE", "OR", "ORB", "ORE", "ORR", "OS", "OTT", "OUR", "OUT", "OVA", "OW", "OWE", "OWL", "OWN", "OX", "PA", "PAD", "PAL", "PAM", "PAN", "PAP", "PAR", "PAT", "PAW", "PAY", "PEA", "PEG", "PEN", "PEP", "PER", "PET", "PEW", "PHI", "PI", "PIE", "PIN", "PIT", "PLY", "PO", "POD", "POE", "POP", "POT", "POW", "PRO", "PRY", "PUB", "PUG", "PUN", "PUP", "PUT", "QUO", "RAG", "RAM", "RAN", "RAP", "RAT", "RAW", "RAY", "REB", "RED", "REP", "RET", "RIB", "RID", "RIG", "RIM", "RIO", "RIP", "ROB", "ROD", "ROE", "RON", "ROT", "ROW", "ROY", "RUB", "RUE", "RUG", "RUM", "RUN", "RYE", "SAC", "SAD", "SAG", "SAL", "SAM", "SAN", "SAP", "SAT", "SAW", "SAY", "SEA", "SEC", "SEE", "SEN", "SET", "SEW", "SHE", "SHY", "SIN", "SIP", "SIR", "SIS", "SIT", "SKI", "SKY", "SLY", "SO", "SOB", "SOD", "SON", "SOP", "SOW", "SOY", "SPA", "SPY", "SUB", "SUD", "SUE", "SUM", "SUN", "SUP", "TAB", "TAD", "TAG", "TAN", "TAP", "TAR", "TEA", "TED", "TEE", "TEN", "THE", "THY", "TIC", "TIE", "TIM", "TIN", "TIP", "TO", "TOE", "TOG", "TOM", "TON", "TOO", "TOP", "TOW", "TOY", "TRY", "TUB", "TUG", "TUM", "TUN", "TWO", "UN", "UP", "US", "USE", "VAN", "VAT", "VET", "VIE", "WAD", "WAG", "WAR", "WAS", "WAY", "WE", "WEB", "WED", "WEE", "WET", "WHO", "WHY", "WIN", "WIT", "WOK", "WON", "WOO", "WOW", "WRY", "WU", "YAM", "YAP", "YAW", "YE", "YEA", "YES", "YET", "YOU", "ABED", "ABEL", "ABET", "ABLE", "ABUT", "ACHE", "ACID", "ACME", "ACRE", "ACTA", "ACTS", "ADAM", "ADDS", "ADEN", "AFAR", "AFRO", "AGEE", "AHEM", "AHOY", "AIDA", "AIDE", "AIDS", "AIRY", "AJAR", "AKIN", "ALAN", "ALEC", "ALGA", "ALIA", "ALLY", "ALMA", "ALOE", "ALSO", "ALTO", "ALUM", "ALVA", "AMEN", "AMES", "AMID", "AMMO", "AMOK", "AMOS", "AMRA", "ANDY", "ANEW", "ANNA", "ANNE", "ANTE", "ANTI", "AQUA", "ARAB", "ARCH", "AREA", "ARGO", "ARID", "ARMY", "ARTS", "ARTY", "ASIA", "ASKS", "ATOM", "AUNT", "AURA", "AUTO", "AVER", "AVID", "AVIS", "AVON", "AVOW", "AWAY", "AWRY", "BABE", "BABY", "BACH", "BACK", "BADE", "BAIL", "BAIT", "BAKE", "BALD", "BALE", "BALI", "BALK", "BALL", "BALM", "BAND", "BANE", "BANG", "BANK", "BARB", "BARD", "BARE", "BARK", "BARN", "BARR", "BASE", "BASH", "BASK", "BASS", "BATE", "BATH", "BAWD", "BAWL", "BEAD", "BEAK", "BEAM", "BEAN", "BEAR", "BEAT", "BEAU", "BECK", "BEEF", "BEEN", "BEER", "BEET", "BELA", "BELL", "BELT", "BEND", "BENT", "BERG", "BERN", "BERT", "BESS", "BEST", "BETA", "BETH", "BHOY", "BIAS", "BIDE", "BIEN", "BILE", "BILK", "BILL", "BIND", "BING", "BIRD", "BITE", "BITS", "BLAB", "BLAT", "BLED", "BLEW", "BLOB", "BLOC", "BLOT", "BLOW", "BLUE", "BLUM", "BLUR", "BOAR", "BOAT", "BOCA", "BOCK", "BODE", "BODY", McDonald [Page 5] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 "BOGY", "BOHR", "BOIL", "BOLD", "BOLO", "BOLT", "BOMB", "BONA", "BOND", "BONE", "BONG", "BONN", "BONY", "BOOK", "BOOM", "BOON", "BOOT", "BORE", "BORG", "BORN", "BOSE", "BOSS", "BOTH", "BOUT", "BOWL", "BOYD", "BRAD", "BRAE", "BRAG", "BRAN", "BRAY", "BRED", "BREW", "BRIG", "BRIM", "BROW", "BUCK", "BUDD", "BUFF", "BULB", "BULK", "BULL", "BUNK", "BUNT", "BUOY", "BURG", "BURL", "BURN", "BURR", "BURT", "BURY", "BUSH", "BUSS", "BUST", "BUSY", "BYTE", "CADY", "CAFE", "CAGE", "CAIN", "CAKE", "CALF", "CALL", "CALM", "CAME", "CANE", "CANT", "CARD", "CARE", "CARL", "CARR", "CART", "CASE", "CASH", "CASK", "CAST", "CAVE", "CEIL", "CELL", "CENT", "CERN", "CHAD", "CHAR", "CHAT", "CHAW", "CHEF", "CHEN", "CHEW", "CHIC", "CHIN", "CHOU", "CHOW", "CHUB", "CHUG", "CHUM", "CITE", "CITY", "CLAD", "CLAM", "CLAN", "CLAW", "CLAY", "CLOD", "CLOG", "CLOT", "CLUB", "CLUE", "COAL", "COAT", "COCA", "COCK", "COCO", "CODA", "CODE", "CODY", "COED", "COIL", "COIN", "COKE", "COLA", "COLD", "COLT", "COMA", "COMB", "COME", "COOK", "COOL", "COON", "COOT", "CORD", "CORE", "CORK", "CORN", "COST", "COVE", "COWL", "CRAB", "CRAG", "CRAM", "CRAY", "CREW", "CRIB", "CROW", "CRUD", "CUBA", "CUBE", "CUFF", "CULL", "CULT", "CUNY", "CURB", "CURD", "CURE", "CURL", "CURT", "CUTS", "DADE", "DALE", "DAME", "DANA", "DANE", "DANG", "DANK", "DARE", "DARK", "DARN", "DART", "DASH", "DATA", "DATE", "DAVE", "DAVY", "DAWN", "DAYS", "DEAD", "DEAF", "DEAL", "DEAN", "DEAR", "DEBT", "DECK", "DEED", "DEEM", "DEER", "DEFT", "DEFY", "DELL", "DENT", "DENY", "DESK", "DIAL", "DICE", "DIED", "DIET", "DIME", "DINE", "DING", "DINT", "DIRE", "DIRT", "DISC", "DISH", "DISK", "DIVE", "DOCK", "DOES", "DOLE", "DOLL", "DOLT", "DOME", "DONE", "DOOM", "DOOR", "DORA", "DOSE", "DOTE", "DOUG", "DOUR", "DOVE", "DOWN", "DRAB", "DRAG", "DRAM", "DRAW", "DREW", "DRUB", "DRUG", "DRUM", "DUAL", "DUCK", "DUCT", "DUEL", "DUET", "DUKE", "DULL", "DUMB", "DUNE", "DUNK", "DUSK", "DUST", "DUTY", "EACH", "EARL", "EARN", "EASE", "EAST", "EASY", "EBEN", "ECHO", "EDDY", "EDEN", "EDGE", "EDGY", "EDIT", "EDNA", "EGAN", "ELAN", "ELBA", "ELLA", "ELSE", "EMIL", "EMIT", "EMMA", "ENDS", "ERIC", "EROS", "EVEN", "EVER", "EVIL", "EYED", "FACE", "FACT", "FADE", "FAIL", "FAIN", "FAIR", "FAKE", "FALL", "FAME", "FANG", "FARM", "FAST", "FATE", "FAWN", "FEAR", "FEAT", "FEED", "FEEL", "FEET", "FELL", "FELT", "FEND", "FERN", "FEST", "FEUD", "FIEF", "FIGS", "FILE", "FILL", "FILM", "FIND", "FINE", "FINK", "FIRE", "FIRM", "FISH", "FISK", "FIST", "FITS", "FIVE", "FLAG", "FLAK", "FLAM", "FLAT", "FLAW", "FLEA", "FLED", "FLEW", "FLIT", "FLOC", "FLOG", "FLOW", "FLUB", "FLUE", "FOAL", "FOAM", "FOGY", "FOIL", "FOLD", "FOLK", "FOND", "FONT", "FOOD", "FOOL", "FOOT", "FORD", "FORE", "FORK", "FORM", "FORT", "FOSS", "FOUL", "FOUR", "FOWL", "FRAU", "FRAY", "FRED", "FREE", "FRET", "FREY", "FROG", "FROM", "FUEL", "FULL", "FUME", "FUND", "FUNK", "FURY", "FUSE", "FUSS", "GAFF", "GAGE", "GAIL", "GAIN", "GAIT", "GALA", "GALE", "GALL", "GALT", "GAME", "GANG", "GARB", "GARY", "GASH", "GATE", "GAUL", "GAUR", "GAVE", "GAWK", "GEAR", "GELD", "GENE", "GENT", "GERM", "GETS", "GIBE", "GIFT", "GILD", "GILL", "GILT", "GINA", "GIRD", "GIRL", "GIST", "GIVE", "GLAD", "GLEE", "GLEN", "GLIB", "GLOB", "GLOM", "GLOW", "GLUE", "GLUM", "GLUT", "GOAD", "GOAL", "GOAT", "GOER", "GOES", "GOLD", "GOLF", "GONE", "GONG", "GOOD", "GOOF", "GORE", "GORY", "GOSH", "GOUT", "GOWN", "GRAB", "GRAD", "GRAY", "GREG", "GREW", "GREY", "GRID", "GRIM", "GRIN", "GRIT", "GROW", McDonald [Page 6] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 "GRUB", "GULF", "GULL", "GUNK", "GURU", "GUSH", "GUST", "GWEN", "GWYN", "HAAG", "HAAS", "HACK", "HAIL", "HAIR", "HALE", "HALF", "HALL", "HALO", "HALT", "HAND", "HANG", "HANK", "HANS", "HARD", "HARK", "HARM", "HART", "HASH", "HAST", "HATE", "HATH", "HAUL", "HAVE", "HAWK", "HAYS", "HEAD", "HEAL", "HEAR", "HEAT", "HEBE", "HECK", "HEED", "HEEL", "HEFT", "HELD", "HELL", "HELM", "HERB", "HERD", "HERE", "HERO", "HERS", "HESS", "HEWN", "HICK", "HIDE", "HIGH", "HIKE", "HILL", "HILT", "HIND", "HINT", "HIRE", "HISS", "HIVE", "HOBO", "HOCK", "HOFF", "HOLD", "HOLE", "HOLM", "HOLT", "HOME", "HONE", "HONK", "HOOD", "HOOF", "HOOK", "HOOT", "HORN", "HOSE", "HOST", "HOUR", "HOVE", "HOWE", "HOWL", "HOYT", "HUCK", "HUED", "HUFF", "HUGE", "HUGH", "HUGO", "HULK", "HULL", "HUNK", "HUNT", "HURD", "HURL", "HURT", "HUSH", "HYDE", "HYMN", "IBIS", "ICON", "IDEA", "IDLE", "IFFY", "INCA", "INCH", "INTO", "IONS", "IOTA", "IOWA", "IRIS", "IRMA", "IRON", "ISLE", "ITCH", "ITEM", "IVAN", "JACK", "JADE", "JAIL", "JAKE", "JANE", "JAVA", "JEAN", "JEFF", "JERK", "JESS", "JEST", "JIBE", "JILL", "JILT", "JIVE", "JOAN", "JOBS", "JOCK", "JOEL", "JOEY", "JOHN", "JOIN", "JOKE", "JOLT", "JOVE", "JUDD", "JUDE", "JUDO", "JUDY", "JUJU", "JUKE", "JULY", "JUNE", "JUNK", "JUNO", "JURY", "JUST", "JUTE", "KAHN", "KALE", "KANE", "KANT", "KARL", "KATE", "KEEL", "KEEN", "KENO", "KENT", "KERN", "KERR", "KEYS", "KICK", "KILL", "KIND", "KING", "KIRK", "KISS", "KITE", "KLAN", "KNEE", "KNEW", "KNIT", "KNOB", "KNOT", "KNOW", "KOCH", "KONG", "KUDO", "KURD", "KURT", "KYLE", "LACE", "LACK", "LACY", "LADY", "LAID", "LAIN", "LAIR", "LAKE", "LAMB", "LAME", "LAND", "LANE", "LANG", "LARD", "LARK", "LASS", "LAST", "LATE", "LAUD", "LAVA", "LAWN", "LAWS", "LAYS", "LEAD", "LEAF", "LEAK", "LEAN", "LEAR", "LEEK", "LEER", "LEFT", "LEND", "LENS", "LENT", "LEON", "LESK", "LESS", "LEST", "LETS", "LIAR", "LICE", "LICK", "LIED", "LIEN", "LIES", "LIEU", "LIFE", "LIFT", "LIKE", "LILA", "LILT", "LILY", "LIMA", "LIMB", "LIME", "LIND", "LINE", "LINK", "LINT", "LION", "LISA", "LIST", "LIVE", "LOAD", "LOAF", "LOAM", "LOAN", "LOCK", "LOFT", "LOGE", "LOIS", "LOLA", "LONE", "LONG", "LOOK", "LOON", "LOOT", "LORD", "LORE", "LOSE", "LOSS", "LOST", "LOUD", "LOVE", "LOWE", "LUCK", "LUCY", "LUGE", "LUKE", "LULU", "LUND", "LUNG", "LURA", "LURE", "LURK", "LUSH", "LUST", "LYLE", "LYNN", "LYON", "LYRA", "MACE", "MADE", "MAGI", "MAID", "MAIL", "MAIN", "MAKE", "MALE", "MALI", "MALL", "MALT", "MANA", "MANN", "MANY", "MARC", "MARE", "MARK", "MARS", "MART", "MARY", "MASH", "MASK", "MASS", "MAST", "MATE", "MATH", "MAUL", "MAYO", "MEAD", "MEAL", "MEAN", "MEAT", "MEEK", "MEET", "MELD", "MELT", "MEMO", "MEND", "MENU", "MERT", "MESH", "MESS", "MICE", "MIKE", "MILD", "MILE", "MILK", "MILL", "MILT", "MIMI", "MIND", "MINE", "MINI", "MINK", "MINT", "MIRE", "MISS", "MIST", "MITE", "MITT", "MOAN", "MOAT", "MOCK", "MODE", "MOLD", "MOLE", "MOLL", "MOLT", "MONA", "MONK", "MONT", "MOOD", "MOON", "MOOR", "MOOT", "MORE", "MORN", "MORT", "MOSS", "MOST", "MOTH", "MOVE", "MUCH", "MUCK", "MUDD", "MUFF", "MULE", "MULL", "MURK", "MUSH", "MUST", "MUTE", "MUTT", "MYRA", "MYTH", "NAGY", "NAIL", "NAIR", "NAME", "NARY", "NASH", "NAVE", "NAVY", "NEAL", "NEAR", "NEAT", "NECK", "NEED", "NEIL", "NELL", "NEON", "NERO", "NESS", "NEST", "NEWS", "NEWT", "NIBS", "NICE", "NICK", "NILE", "NINA", "NINE", "NOAH", "NODE", "NOEL", "NOLL", "NONE", "NOOK", "NOON", "NORM", "NOSE", "NOTE", "NOUN", "NOVA", "NUDE", "NULL", "NUMB", "OATH", "OBEY", McDonald [Page 7] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 "OBOE", "ODIN", "OHIO", "OILY", "OINT", "OKAY", "OLAF", "OLDY", "OLGA", "OLIN", "OMAN", "OMEN", "OMIT", "ONCE", "ONES", "ONLY", "ONTO", "ONUS", "ORAL", "ORGY", "OSLO", "OTIS", "OTTO", "OUCH", "OUST", "OUTS", "OVAL", "OVEN", "OVER", "OWLY", "OWNS", "QUAD", "QUIT", "QUOD", "RACE", "RACK", "RACY", "RAFT", "RAGE", "RAID", "RAIL", "RAIN", "RAKE", "RANK", "RANT", "RARE", "RASH", "RATE", "RAVE", "RAYS", "READ", "REAL", "REAM", "REAR", "RECK", "REED", "REEF", "REEK", "REEL", "REID", "REIN", "RENA", "REND", "RENT", "REST", "RICE", "RICH", "RICK", "RIDE", "RIFT", "RILL", "RIME", "RING", "RINK", "RISE", "RISK", "RITE", "ROAD", "ROAM", "ROAR", "ROBE", "ROCK", "RODE", "ROIL", "ROLL", "ROME", "ROOD", "ROOF", "ROOK", "ROOM", "ROOT", "ROSA", "ROSE", "ROSS", "ROSY", "ROTH", "ROUT", "ROVE", "ROWE", "ROWS", "RUBE", "RUBY", "RUDE", "RUDY", "RUIN", "RULE", "RUNG", "RUNS", "RUNT", "RUSE", "RUSH", "RUSK", "RUSS", "RUST", "RUTH", "SACK", "SAFE", "SAGE", "SAID", "SAIL", "SALE", "SALK", "SALT", "SAME", "SAND", "SANE", "SANG", "SANK", "SARA", "SAUL", "SAVE", "SAYS", "SCAN", "SCAR", "SCAT", "SCOT", "SEAL", "SEAM", "SEAR", "SEAT", "SEED", "SEEK", "SEEM", "SEEN", "SEES", "SELF", "SELL", "SEND", "SENT", "SETS", "SEWN", "SHAG", "SHAM", "SHAW", "SHAY", "SHED", "SHIM", "SHIN", "SHOD", "SHOE", "SHOT", "SHOW", "SHUN", "SHUT", "SICK", "SIDE", "SIFT", "SIGH", "SIGN", "SILK", "SILL", "SILO", "SILT", "SINE", "SING", "SINK", "SIRE", "SITE", "SITS", "SITU", "SKAT", "SKEW", "SKID", "SKIM", "SKIN", "SKIT", "SLAB", "SLAM", "SLAT", "SLAY", "SLED", "SLEW", "SLID", "SLIM", "SLIT", "SLOB", "SLOG", "SLOT", "SLOW", "SLUG", "SLUM", "SLUR", "SMOG", "SMUG", "SNAG", "SNOB", "SNOW", "SNUB", "SNUG", "SOAK", "SOAR", "SOCK", "SODA", "SOFA", "SOFT", "SOIL", "SOLD", "SOME", "SONG", "SOON", "SOOT", "SORE", "SORT", "SOUL", "SOUR", "SOWN", "STAB", "STAG", "STAN", "STAR", "STAY", "STEM", "STEW", "STIR", "STOW", "STUB", "STUN", "SUCH", "SUDS", "SUIT", "SULK", "SUMS", "SUNG", "SUNK", "SURE", "SURF", "SWAB", "SWAG", "SWAM", "SWAN", "SWAT", "SWAY", "SWIM", "SWUM", "TACK", "TACT", "TAIL", "TAKE", "TALE", "TALK", "TALL", "TANK", "TASK", "TATE", "TAUT", "TEAL", "TEAM", "TEAR", "TECH", "TEEM", "TEEN", "TEET", "TELL", "TEND", "TENT", "TERM", "TERN", "TESS", "TEST", "THAN", "THAT", "THEE", "THEM", "THEN", "THEY", "THIN", "THIS", "THUD", "THUG", "TICK", "TIDE", "TIDY", "TIED", "TIER", "TILE", "TILL", "TILT", "TIME", "TINA", "TINE", "TINT", "TINY", "TIRE", "TOAD", "TOGO", "TOIL", "TOLD", "TOLL", "TONE", "TONG", "TONY", "TOOK", "TOOL", "TOOT", "TORE", "TORN", "TOTE", "TOUR", "TOUT", "TOWN", "TRAG", "TRAM", "TRAY", "TREE", "TREK", "TRIG", "TRIM", "TRIO", "TROD", "TROT", "TROY", "TRUE", "TUBA", "TUBE", "TUCK", "TUFT", "TUNA", "TUNE", "TUNG", "TURF", "TURN", "TUSK", "TWIG", "TWIN", "TWIT", "ULAN", "UNIT", "URGE", "USED", "USER", "USES", "UTAH", "VAIL", "VAIN", "VALE", "VARY", "VASE", "VAST", "VEAL", "VEDA", "VEIL", "VEIN", "VEND", "VENT", "VERB", "VERY", "VETO", "VICE", "VIEW", "VINE", "VISE", "VOID", "VOLT", "VOTE", "WACK", "WADE", "WAGE", "WAIL", "WAIT", "WAKE", "WALE", "WALK", "WALL", "WALT", "WAND", "WANE", "WANG", "WANT", "WARD", "WARM", "WARN", "WART", "WASH", "WAST", "WATS", "WATT", "WAVE", "WAVY", "WAYS", "WEAK", "WEAL", "WEAN", "WEAR", "WEED", "WEEK", "WEIR", "WELD", "WELL", "WELT", "WENT", "WERE", "WERT", "WEST", "WHAM", "WHAT", "WHEE", "WHEN", "WHET", "WHOA", "WHOM", "WICK", "WIFE", "WILD", "WILL", "WIND", "WINE", "WING", "WINK", "WINO", "WIRE", "WISE", "WISH", McDonald [Page 8] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 "WITH", "WOLF", "WONT", "WOOD", "WOOL", "WORD", "WORE", "WORK", "WORM", "WORN", "WOVE", "WRIT", "WYNN", "YALE", "YANG", "YANK", "YARD", "YARN", "YAWL", "YAWN", "YEAH", "YEAR", "YELL", "YOGA", "YOKE" }; /* Encode 8 bytes in 'c' as a string of English words. * Returns a pointer to a static buffer */ char * btoe(engout,c) char *c, *engout; { char cp[9]; /* add in room for the parity 2 bits*/ int p,i ; engout[0] = '\0'; memcpy(cp, c,8); /* compute parity */ for(p = 0,i = 0; i < 64;i += 2) p += extract(cp,i,2); cp[8] = (char)p << 6; strncat(engout,&Wp[extract(cp, 0,11)][0],4); strcat(engout," "); strncat(engout,&Wp[extract(cp,11,11)][0],4); strcat(engout," "); strncat(engout,&Wp[extract(cp,22,11)][0],4); strcat(engout," "); strncat(engout,&Wp[extract(cp,33,11)][0],4); strcat(engout," "); strncat(engout,&Wp[extract(cp,44,11)][0],4); strcat(engout," "); strncat(engout,&Wp[extract(cp,55,11)][0],4); #ifdef notdef printf("engout is %s\n\r",engout); #endif return(engout); } /* convert English to binary * returns 1 OK - all good words and parity is OK * 0 word not in data base * -1 badly formed in put ie > 4 char word * -2 words OK but parity is wrong */ int etob(out, e) char *out; McDonald [Page 9] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 char *e; { char *word; int i, p, v,l, low,high; char b[9]; char input[36]; if(e == NULL) return -1; strncpy(input,e,sizeof(input)); memset(b, 0, sizeof(b)); memset(out, 0, 8); for(i=0,p=0;i<6;i++,p+=11){ if((word = strtok(i == 0 ? input : NULL," ")) == NULL) return -1; l = strlen(word); if(l > 4 || l < 1){ return -1; } else if(l < 4){ low = 0; high = 570; } else { low = 571; high = 2047; } standard(word); if( (v = wsrch(word,low,high)) < 0 ) return 0; insert(b,v,p,11); } /* now check the parity of what we got */ for(p = 0, i = 0; i < 64; i +=2) p += extract(b, i, 2); if( (p & 3) != extract(b, 64,2) ) return -2; memcpy(out,b,8); return 1; } /* Display 8 bytes as a series of 16-bit hex digits */ char * put8(out,s) char *out; char *s; McDonald [Page 10] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 { sprintf(out,"%02X%02X %02X%02X %02X%02X %02X%02X", s[0] & 0xff,s[1] & 0xff,s[2] & 0xff, s[3] & 0xff,s[4] & 0xff,s[5] & 0xff, s[6] & 0xff,s[7] & 0xff); return out; } #ifdef notdef /* Encode 8 bytes in 'cp' as stream of ascii letters. * Provided as a possible alternative to btoe() */ char * btoc(cp) char *cp; { int i; static char out[31]; /* code out put by characters 6 bits each added to 0x21 (!)*/ for(i=0;i <= 10;i++){ /* last one is only 4 bits not 6*/ out[i] = '!'+ extract(cp,6*i,i >= 10 ? 4:6); } out[i] = '\0'; return(out); } #endif /* Internal subroutines for word encoding/decoding */ /* Dictionary binary search */ static int wsrch(w,low,high) char *w; int low, high; { int i,j; for(;;){ i = (low + high)/2; if((j = strncmp(w,Wp[i],4)) == 0) return i; /* Found it */ if(high == low+1){ /* Avoid effects of integer truncation in /2 */ if(strncmp(w,Wp[high],4) == 0) return high; else return -1; McDonald [Page 11] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 } if(low >= high) return -1; /* I don't *think* this can happen...*/ if(j < 0) high = i; /* Search lower half */ else low = i; /* Search upper half */ } } static void insert(s, x, start, length) char *s; int x; int start, length; { unsigned char cl; unsigned char cc; unsigned char cr; unsigned long y; int shift; assert(length <= 11); assert(start >= 0); assert(length >= 0); assert(start +length <= 66); shift = ((8 -(( start + length) % 8))%8); y = (long) x << shift; cl = (y >> 16) & 0xff; cc = (y >> 8) & 0xff; cr = y & 0xff; if(shift + length > 16){ s[start /8] |= cl; s[start/8 +1] |= cc; s[start/8 +2] |= cr; } else if(shift +length > 8){ s[start/8] |= cc; s[start/8 + 1] |= cr; } else { s[start/8] |= cr; } } static void standard(word) register char *word; { while(*word){ McDonald [Page 12] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 if(!isascii(*word)) break; if(islower(*word)) *word = toupper(*word); if(*word == '1') *word = 'L'; if(*word == '0') *word = 'O'; if(*word == '5') *word = 'S'; word++; } } /* Extract 'length' bits from the char array 's' starting with bit 'start' */ static unsigned long extract(s, start, length) char *s; int start, length; { unsigned char cl; unsigned char cc; unsigned char cr; unsigned long x; assert(length <= 11); assert(start >= 0); assert(length >= 0); assert(start +length <= 66); cl = s[start/8]; cc = s[start/8 +1]; cr = s[start/8 +2]; x = ((long)(cl<<8 | cc) <<8 | cr) ; x = x >> (24 - (length + (start %8))); x =( x & (0xffff >> (16-length) ) ); return(x); } McDonald [Page 13] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 Appendix B - Source for 128-bit key to/from English words (convert.c) /* convert.c -- Wrapper to S/Key binary-to-English routines. Daniel L. McDonald -- U. S. Naval Research Laboratory. */ #include <string.h> /* eng2key() assumes words must be separated by spaces only. eng2key() returns 1 if succeeded 0 if word not in dictionary -1 if badly formed string -2 if words are okay but parity is wrong. (see etob() in S/Key) */ int eng2key(keyout,eng) char *keyout,*eng; { int rc=0,state=1; char *eng2; /* Find pointer to word 7. */ for (eng2 = eng; rc<7 && (*(++eng2) != '\0'); ) if (*eng2 != ' ') { rc += state; state = 0; } else state=1; if ( (rc = etob(keyout,eng)) != 1) return rc; rc = etob(keyout+8,eng2); return rc; } /* key2eng() assumes string referenced by engout has at least 60 characters (4*12 + 11 spaces + '\0') of space. key2eng() returns pointer to engout. */ McDonald [Page 14] INTERNET-DRAFT Human-Readable 128-bit Keys 20 August 1994 char *key2eng(engout,key) char *engout,*key; { btoe(engout,key); strcat(engout," "); btoe(engout+strlen(engout),key+8); } McDonald [Page 15]