From: "Olivier D." <purple.dot_meteor@..._dot.com>
Date: 2004-09-10T04:00:42+09:00
Subject: Re: Réf. : ASCII, RSA AND BIGNUM

Be careful, I'm a nuby, but I've found a few things:

On 2004-09-09, Barry Sperling <barry@angleinc.com> wrote:
> # PRINTS ASCII OF ARRAY, CURRENTLY BACKWARDS AND 8 CHARACTERS SPECIFICALLY
> def convert_to_text( num )
> ...
> end

If you want to convert ASCII chars from 0 to 99 in one line, you can do:

def convert_to_text(num)
    num.to_s.reverse.scan(/\d\d?/).map { |c|
        c.reverse.to_i.chr
    }.join.reverse
end

BUT it's dirty and you're limited to decimal values <= 99.
Why not use String#hex instead:

# give this function an hexa string
def hex_to_text(string)
    string.scan(/../).map { |c| c.hex.chr }.join
end
puts hex_to_text("61626364")

> # THE TEXT, TO BE ENCRYPTED AND SENT ALONG WITH THE PUBLIC KEY
> #  LIMITED TO 8 CHAR, ALL WITH ASCII VALUES BELOW 100
> s = "GO SKINS"
> asc_of_text = 0
> s.each_byte do |a|   #TAKING EACH CHAR AS A 2-DIGIT NUM AND CREATING A
>    print( a ); print( ' ' )     # LARGE NUM WITH EACH PAIR OF DIGITS
> 				# BEING THE ASCII
>    asc_of_text *= 100          # OF THE STRING, LEFT-MOST 2 DIGITS BEING
> 				#THE FIRST LETTER
>    asc_of_text += a
> end
> puts

You can do this shorter:

s = "GO SKINS"
asc = s.split(//).map { |c| "%02d" % c[0] }.join

No comments for the crypto part, I'll have to read my lessons again...

And a last comment for the code: remove all the for loops, like
for i in 0..(string.length - 1) and change them into 'each' calls with
blocks associated.

With Strings you can use 'each'.
With Arrays you can use 'each', 'each_index'.
And with all the Enumerables (String, Array...): each_with_index.

-- 
Olivier D.