abomination: Spritz/RS14 in portable /bin/sh

Spritz.sh

#! /bin/sh
# "Spritz - a spongy RC4-like stream cipher and hash function"
# http://people.csail.mit.edu/rivest/pubs/RS14.bib.txt

# In case you're insane enough to use it, keep in mind that the registers
# (i,j,...) have NO PREFIX, so you'll have to add it(_spritz_i, ...).
# This script is meant to run on any POSIX shell with local variables
# ("local" is not included in POSIX. Idiots!) and POSIX commands (printf(1)).

# Bash,dash,mksh,zsh: see how fast they Absorb()/Drip() compared to vim...

# seq(1) is from plan9; linux/freebsd have it, openbsd does not.
seq() {
        # zsh, seq 512: "job table full or recursion limit exceeded"
        test $# -eq 1 && { seq 0 $1; return; }
        test $# -eq 2 || { echo>&2 "seq!"; exit 100; }
        test $1 -ge $2 || { echo $1; seq $((1 + $1)) $2; }
}
seq() {
        test $# -eq 1 && { seq 0 $1; return; }
        test $# -eq 2 || { echo>&2 "seq!"; exit 100; }
        local n=$1
        while [ $n -lt $2 ] ; do echo $n; n=$(($n + 1)) ; done
}

Swap() {
        # S is implicit, params are the two indexes
        local temp
        eval "temp=\$S$1"
        eval "S$1=\$S$2"
        eval "S$2=$temp"
}

InitializeState() {
        i=0
        j=0
        k=0
        z=0
        a=0
        w=1
        for v in $(seq 256) ; do
                eval S"$v=$v"
        done
}

Absorb() {
        for v in "$@" ; do
                AbsorbByte $v
        done
}

AbsorbByte() {
        AbsorbNibble $((0xF & $1))
        AbsorbNibble $((0xF & ($1 >> 4) ))
}

AbsorbNibble() {
        if [ $a -eq 128 ] ; then
                Shuffle
        fi
        Swap $a $((128 + $1))
        a=$(($a + 1))
}

AbsorbStop() {
        if [ $a -eq 128 ] ; then
                Shuffle
        fi
        a=$(($a + 1))
}

Shuffle() {
        Whip 512
        Crush
        Whip 512
        Crush
        Whip 512
        a=0
}

Whip() {
        for v in $(seq $1) ; do
                Update
        done
        w=$(($w + 2))
        w=$(($w & 0xFF))
}

Crush() {
        for v in $(seq 128) ; do
                # if $[v] > S[N-1-v]
                local N1v=$((256 - 1 - $v))
                eval "test \$S$v -gt \$S$N1v" && Swap $v $N1v
        done
}

# Squeeze() in /bin/sh is too ugly, even for me.
Drip() {
        if [ $a -gt 0 ] ; then
                Shuffle
        fi
        Update
        # z = S[j + S[i + S[z + k]]]
        local Szk
        zk=$((0xFF & ($z+$k) ))
        eval "Szk=\$S$zk"
        local iS=$((0xFF & ($i + $Szk) ))
        local Si
        eval "Si=\$S$iS"
        local jS=$((0xFF & ($j + $Si) ))
        eval "z=\$S$jS"
        return $z       # POSIX says this is ok.
}

Update() {
        i=$((0xFF & ($i + $w) ))
        # j = 0xFF &(k + S[0xFF &(j + S[i])]);
        eval "local jSi=\$(($j + \$S$i))" ; jSi=$((0xFF & $jSi))
        eval "local SjSi=\$S$jSi"
        j=$((0xFF & ($k + $SjSi) ))
        # k = 0xFF &(i + k + S[j]);
        eval "local Sj=\$S$j"
        k=$((0xFF & ($i + $k + $Sj) ))
        Swap $i $j
}

# "If the value of n is greater than 255, the results are undefined"
retcheck() {
        return $1
}
for i in $(seq 256)  ; do
        retcheck $i
        j=$?
        test $i = $j&&continue
        echo>&2 "canthappen: return $i yields $j..."
        exit 123
done

if [ x"$NDEBUG" = x ] ; then
        echo "Checking Spritz/RS14 test vectors..."
        # Test stream cipher
        InitializeState
        Absorb 0x41 0x42 0x43   # "ABC"
        for byte in q w e r t y u i ; do
                Drip
                printf %02x $?
        done
        echo
        echo '77 9a 8e 01 f9 e9 cb c0 ... # streamcipher("ABC")'

        # Test hash function
        InitializeState
        Absorb 0x41 0x42 0x43   # "ABC"
        AbsorbStop
        Absorb 32       # 256 bit => 32 bytes, as specified in the paper.
        for byte in q w e r t y u i ; do
                Drip
                printf %02x $?
        done
        echo
        echo '02 8f a2 b4 8b 93 4a 18 ... # hash("ABC")'
fi

# Reset ^^
InitializeState