gistfile1.txt

module BlockTEA

	

	#

	# encrypt: Use Corrected Block TEA to encrypt plaintext using password

	# Return encrypted text as string

	#

	def encrypt(plaintext, password)

		if plaintext.length == 0

			return('')  # nothing to encrypt

		end

		

		# 'escape' plaintext so chars outside ISO-8859-1 work in single-byte packing, but  

		# keep spaces as spaces (not '%20') so encrypted text doesn't grow too long, and 

		# convert result to longs

#		v = strToLongs(escape(plaintext).gsub(/%20/,' '))

		v = strToLongs(plaintext)

		if v.length == 1

			v[1] = 0  # algorithm doesn't work for n<2 so fudge by adding nulls

		end

		k = strToLongs(password.ljust(16).slice(0,16))  # simply convert first 16 chars of password as key

		n = v.length

	

		z = v[n-1]

		y = v[0]

		delta = 0x9E3779B9

		#mx, e

		sum = 0

	

		(6 + 52.0/n).floor.downto(1) { |q|  # 6 + 52/n operations gives between 6 & 32 mixes on each word

			sum = (sum + delta) & 0xffffffff

			e = sum>>2 & 3

			for p in (0...n-1)

				y = v[p+1]

				mx = ((z>>5 ^ ((y<<2)&0xffffffff)) + (y>>3 ^ ((z<<4)&0xffffffff)) ^ (sum^y) + (k[p&3 ^ e] ^ z)) & 0xffffffff

				v[p] = (v[p] + mx) & 0xffffffff

				z = v[p]

			end

			y = v[0]

			mx = ((z>>5 ^ ((y<<2)&0xffffffff)) + (y>>3 ^ ((z<<4)&0xffffffff)) ^ (sum^y) + (k[(n-1)&3 ^ e] ^ z)) & 0xffffffff

			v[n-1] = (v[n-1] + mx) & 0xffffffff

			z = v[n-1]

		}

	

		ciphertext = longsToStr(v)

	

		return ciphertext.unpack('a*').pack('m').delete("\n") # base64 encode it without newlines

	end

	

	#

	# decrypt: Use Corrected Block TEA to decrypt ciphertext using password

	#

	def decrypt(ciphertext, password)

		if ciphertext.length == 0

			return('')

		end

		

		v = strToLongs(ciphertext.unpack('m').pack("a*"))	# base64 decode and convert to array of 'longs'

		k = strToLongs(password.ljust(16).slice(0,16))

		n = v.length

	

		z = v[n-1]

		y = v[0]

		delta = 0x9E3779B9

		#mx, e

		q = (6 + 52.0/n).floor

		sum = q*delta

		

		while (sum > 0)

			e = sum>>2 & 3

			(n-1).downto(1) { |p|

				z = v[p-1]

				mx = ((z>>5 ^ ((y<<2)&0xffffffff)) + (y>>3 ^ ((z<<4)&0xffffffff)) ^ (sum^y) + (k[p&3 ^ e] ^ z)) & 0xffffffff

				v[p] = (v[p] - mx) & 0xffffffff

				y = v[p]

			}

			z = v[n-1]

			mx = ((z>>5 ^ ((y<<2)&0xffffffff)) + (y>>3 ^ ((z<<4)&0xffffffff)) ^ (sum^y) + (k[0 ^ e] ^ z)) & 0xffffffff

			v[0] = (v[0] - mx) & 0xffffffff

			y = v[0]

			sum -= delta

		end

	

		plaintext = longsToStr(v)

	

		# strip trailing null chars resulting from filling 4-char blocks:

		plaintext = plaintext.gsub(/\0+$/,'')

	

		return plaintext

	end

	

	

	# supporting functions

	

	def strToLongs(s)

		s << [0,0,0].pack('c*') # Pad with at most three nulls

		return s.unpack('L*')

	end

	

	def longsToStr(l)   # convert array of longs back to string

		l.pack('L*')

	end

	

	module_function :encrypt, :decrypt, :strToLongs, :longsToStr

end