#!/bin/ksh
# NAME:		obfuscate -- obfuscate text read from one or more files into a
#			     string that can be decrypted by the dc utility
#
# SYNOPSIS:	obfuscate file...
#
# OPERANDS:	file	The name of a text file containing text to be
#			obfuscated or "-" to obfuscate text read from
#			standard input.
#
# APPLICATION USAGE:
#	To decrypt the obfuscated string produced by obfuscate, use:
#		obfuscate file | read string	# Get obfuscated text
# 	Note: Do not use "read -r string" in the above command!
#		printf '%s\n' "$string"		# Show obfuscated text
#		echo "$string" | dc		# Decrypt obfuscated text
#
#	Although dc can produce artibrary length output, feeding the objuscated
#	string back into dc for decryption may be limited by {LINE_MAX} and/or
#	{ARG_MAX} restrictions.

# Initialize a to ASCII character set (skipping NUL)...
a='\1\2\3\4\5\6\7\10\11\12\13\14\15\16\17\20\21\22\23\24\25\26\27\30\31\32\33'
a="$a"'\34\35\36\37 !"#$%&'"'"'()*+,-./0123456789:;<=>?@'
a="$a"'ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\377'

awk -v A="$a" '
function cline(inline,		i) {
	printf("256*%d+\n", index(A, "\n"))
	for(i = length(inline); i; i--) {
		printf("256*%d+\n", index(A, substr(inline, i, 1)))
	}
}
BEGIN {	print 0
}
{	line[NR] = $0
}
END {	for(i = NR; i; i--)
		cline(line[i])
	printf("[[q]sa[ln0=aln256%%Pln256/snlbx]sb]Pn[snlbxq\n]Pq\n")
}' "$@" | tee .dc_input | dc

chmod +x obfuscate

printf "Hello World.\nAre we there yet?\nLet's go home, now!\n" | ./obfuscate - | read string

echo "$string"

[q]sa[ln0=aln256%Pln256/snlbx]sb26160072918627741401952510855241017735603346265259888938898171600856988789569756293233903076568696999873394858335331444040snlbxq

echo "$string"|dc

Hello World.
Are we there yet?
Let's go home, now!

awk: can't open file -

printf "Hello World.\nAre we there yet?\nLet's go home, now!\n" > ob$$
./obfuscate ob$$ | read string
rm -f ob$$

cat .dc_input

0
256*10+
256*33+
256*119+
256*111+
256*110+
256*32+
256*44+
256*101+
256*109+
256*111+
256*104+
256*32+
256*111+
256*103+
256*32+
256*115+
256*39+
256*116+
256*101+
256*76+
256*10+
256*63+
256*116+
256*101+
256*121+
256*32+
256*101+
256*114+
256*101+
256*104+
256*116+
256*32+
256*101+
256*119+
256*32+
256*101+
256*114+
256*65+
256*10+
256*46+
256*100+
256*108+
256*114+
256*111+
256*87+
256*32+
256*111+
256*108+
256*108+
256*101+
256*72+
[[q]sa[ln0=aln256%Pln256/snlbx]sb]Pn[snlbxq
]Pq