I wrote up the ruby script below to help my students understand public key encryption. I followed the "pencil and paper" method shown here: http://sergematovic.tripod.com/rsa1.html
This works fine as long as 29 isn't chosen as either p or q. If 29 is picked, it hangs on calculating the secret key. Can anyone tell me why that is?
#!/usr/bin/env ruby -wKU
#initialize
primes, p, q, n, z, k, j, m,e,d = nil
def prime
primes = [2,3,5,7,11,13,17,19,23,29,31]
primes.sample
end
#pick p
p= prime
puts "p: " + p.to_s
#pick q
q=p
while p==q
q = prime
end
puts "q: " + q.to_s
#find n
n=p*q
puts "n: " + n.to_s
#find z
z=(p-1)*(q-1)
puts "z: " + z.to_s
#pick a relative prime of the totient
k=7
puts "k: " + k.to_s
#calculate secret key
j=0
while j*k % z != 1
j+=1
end
puts "j: " + j.to_s
#message
m=16
puts "Message: " + m.to_s
#encrypt
e = m**k % n
puts "Encrypted: " + e.to_s
#decrypt
d = e**j % n
puts "Decrypted: " + d.to_s
When 29 is chosen as p or q, z has 28 as a factor, and thus k = 7 is not a relative prime of the totient as your comment claims!
(This means j*k % z is always a multiple of 7, so your loop never terminates.)
Related
Trying to create a ceaser cipher in Ruby.
The problem I'm facing is that when the program reaches the while loop, it only performs the desired operation on the very last letter of the inputted word. Before I delve further into what I've tried, please find the code:
#!/usr/bin/ruby
#print 65.chr ASCII code for A
#print 97.chr ASCII code for a
a = 0
b = 97
d = []
e = 0
# Just to print the alphabet alongside the ASCII value
# (For sanity checking)
while a <= 25
print b.chr + " "
print b.to_s + "\n"
a = a + 1
b = b + 1
end
puts "\n Please enter a word to translate"
word = gets.strip
# The desired effect is to move the letter along by key value
puts "Please enter a key"
k = gets.chomp.to_i
# In its current state, what happens is only the last char
# is moved along by the key value.
while e <= word.length
word.each_byte do |c|
d[e] = c + k
end
e = e + 1
end
puts d
I'm thinking that the problem lies with the logic for the while loop. The way I am going to attack this is by reading the pre-converted word into an array, as opposed to using the .each_byte object.
I don't know how to do that and the guides/questions I've found don't quite answer the question. If anyone knows how to do this, or knows a better way of solving this- I'd be much appreciative.
you don't need the last while loop
word.each_byte do |c|
d[e] = c + k
e = e + 1
end
Something a bit more verbose:
alphabet = ('a'..'z').to_a
new_word = ''
puts "\n Please enter a word to translate"
word = gets.strip
puts "Please enter a key"
k = gets.chomp.to_i
word.split('').each_with_index do |letter, index|
alphabet_index = alphabet.index(letter)
new_index = alphabet_index + key
new_word[index] = alphabet[new_index]
end
puts "Your translated word is #{new_word}"
Caesar cipher is a simple shift cipher
word.each_byte do |c|
p c + k
end
Managed to get it working, thanks for all the help... Code for anyone interested:
#!/usr/bin/ruby
#print 65.chr A
#print 97.chr a
a = 0
b = 65
y = 97
d = []
e = 0
while a <= 25
print y.chr + " = " + y.to_s + " "
print b.chr + " = " + b.to_s + " " + "\n"
a = a + 1
b = b + 1
y = y + 1
end
puts "\n Please enter a word to translate"
word = gets.strip
puts "Please enter a key"
k = gets.chomp.to_i
word.each_byte do |c|
d[e] = c + k
e = e + 1
end
print "\n"
a = 0
arlen = d.count
while a != arlen
print d[a].chr
a = a + 1
end
print k
This question already has answers here:
What is the difference between a constant and a variable in Ruby?
(3 answers)
Closed 6 years ago.
Here's my code:
puts "Input a number."
Divisor = 2
inputNumber = gets.chomp
if inputNumber.to_i == 1 || inputNumber.to_i == 2
if inputNumber.to_i == 1
puts inputNumber + " is not a prime."
else
puts inputNumber + " is a prime."
end
else
while Divisor.to_i < inputNumber.to_i
if inputNumber.to_i%Divisor.to_i == 0
puts inputNumber + " is not a Prime as " + Divisor.to_s + " is a factor."
break
else
Divisor = Divisor.to_i + 1
end
end
puts inputNumber + " is a prime!"
end
I got the following error:
test1.rb:30: warning: already initialized constant Divisor
test1.rb:3: warning: previous definition of Divisor was here
What is wrong?
Constants and variables
Divisor is a constant. You want a variable : divisor. See this answer.
Notes
puts inputNumber + " is a prime!" is always called.
You could replace break by exit, or use a boolean variable.
Since you work with numbers, you could also call .to_i once, do your calculation, and just use .to_s to display results
You only have to check for factors in the range (2..Math.sqrt(inputNumber))
You don't have to check twice if inputNumber == 1
puts 'Input a number.'
divisor = 2
inputNumber = gets.chomp.to_i
prime = true
if inputNumber == 1
puts inputNumber.to_s + ' is not a prime.'
else
while divisor <= Math.sqrt(inputNumber)
if inputNumber % divisor == 0
puts inputNumber.to_s + ' is not a Prime as ' + divisor.to_s + ' is a factor.'
prime = false
break
else
divisor += 1
end
end
puts inputNumber.to_s + ' is a prime!' if prime
end
Alternative
A shorter alternative can be written with Enumerable#find. It executes the block with every element, stops as soon as the code in block returns a truthy value, and returns the element for which the block is truthy. If no element is found, it returns nil :
puts 'Input a number.'
number = gets.chomp.to_i
divisor = (2..Math.sqrt(number)).find { |i| number % i == 0 }
if number == 1
puts '1 is not a prime.'
elsif divisor
puts format('%d is not a prime as %d is a factor.', number, divisor)
else
puts format('%d is a prime!', number)
end
I'm trying to do in the Ruby program the summation of a factorial. and I can not solve. a clarification, when they run out points .... means that the logic is fine. if you get a F in one of the points, it means that the logic is wrong.
Write a program to calculate the sum of 1 + 1 / (2!) + 1 / (3!) + 1 / (4!) + .... + 1 / (n!) For a given n. Write the program in two ways: using While, For
def factorial(n)
#(n == 0) ? 1 : n * factorial(n - 1)
fact = 1
for i in 1..n
fact = fact * i
end
return fact
end
def sumatoriaWhile(n)
total = n
sumatoria = 0.0
while n > 1
total = total * (n - 1)
n = n - 1
sumatoria =sumatoria + total.to_f
end
return (1 + (1 / total.to_f)).round(2)
end
def sumatoriaFor(n)
fact = 1
sumatoria = 0.0
for i in 1..n
for j in 1..i
fact = fact * j
end
sumatoria = sumatoria + (1 / fact.to_f)
i = i + 1
end
return sumatoria.round(2)
end
#--- zona de test ----
def test_factorial
print validate(120, factorial(5))
print validate(5040, factorial(7))
print validate(362880, factorial(9))
end
def test_sumatoriaWhile
print validate(1.50, sumatoriaWhile(2))
print validate(1.83, sumatoriaWhile(3))
end
def test_sumatoriaFor
print validate(1.50, sumatoriaFor(2))
print validate(1.83, sumatoriaFor(3))
end
def validate (expected, value)
expected == value ? "." : "F"
end
def test
puts "Test program"
puts "---------------------------"
test_factorial
test_sumatoriaWhile
test_sumatoriaFor
puts " "
end
test
My friend, Thank you for your prompt response. First of all, I appreciate the help given. I am learning ruby programming and want to learn more as you and the other people. if indeed the answer is wrong. I have modified the answer. and also need to know what the function of While. and I hereby amended program again. and now I get an F on the part of WHILE.
def factorial(n)
fact = 1
for i in 1..n
fact = fact * i
end
return fact
end
def sumatoriaWhile(n)
total = n
sumatoria = 0.0
while n < 1
total = total * (n - 1)
sumatoria = sumatoria + (1.0 / total.to_f)
n = n - 1
end
return sumatoria.round(2)
end
def sumatoriaFor(n)
fact = 1
sumatoria = 0.0
for i in 1..n
fact = fact * i
sumatoria = sumatoria + (1.0 / fact.to_f)
end
return sumatoria.round(2)
end
#--- zona de test ----
def test_factorial
print validate(120, factorial(5))
print validate(5040, factorial(7))
print validate(362880, factorial(9))
end
def test_sumatoriaWhile
print validate(1.50, sumatoriaWhile(2))
print validate(1.67, sumatoriaWhile(3))
end
def test_sumatoriaFor
print validate(1.50, sumatoriaFor(2))
print validate(1.67, sumatoriaFor(3))
end
def validate (expected, value)
expected == value ? "." : "F"
end
def test
puts "Test de prueba del programa"
puts "---------------------------"
test_factorial
test_sumatoriaWhile
test_sumatoriaFor
puts " "
end
test
I have a hard time figuring out what you're doing in the summation function. Here's a straightforward function:
def sumatoriaFor(n)
return 0 if n <= 0
factorial = 1
sum = 0.0
for i in 1..n
factorial *= i
sum += 1.0 / factorial.to_f
end
return sum.round(2)
end
def sumatoriaWhile(n)
return 0 if n <= 0
i = 1
factorial = 1
sumatoria = 0.0
while i <= n
factorial *= i
sumatoria += (1.0 / factorial.to_f)
i = i + 1
end
return sumatoria.round(2)
end
The while look is straight forward too now. Also your validation is wrong:
1 + 1/2 + 1/6 ~= 1 + 0.5 + 0.17 = 1.67
I'm asked to write the ruby program that generate the output based the given command,
The full description
I'm really new in ruby (maybe few hours that I have started ruby)
When I run the program I get into infinite loop, I don't understand why.
Thank you.
What I have done so far:
# MyVector Class
class MyVector
def initialize (a)
if !(a.instance_of? Array)
raise "ARGUMENT OF INITIALIZER MUST BE AN ARRAY"
else
#array = a
end
end
def array
#array
end
def to_s
#array.to_s
end
def length
#array.length
end
def [](i)
#array[i]
end
def each2(a)
raise Error, "INTEGER IS NOT LIKE VECTOR" if a.kind_of?(Integer)
Vector.Raise Error if length != a.length
return to_enum(:each2, a) unless block_given?
length.times do |i|
yield #array[i], a[i]
end
self
end
def * (a)
Vector.Raise Error if length != a.length
p = 0
each2(a) {|a1, a2|p += a1 * a2}
p
end
end
# MyMatrix Class
class MyMatrix
def initialize a
#array=Array.new(a.length)
i=0
while(i<a.length)
#array[i]=MyVector.new(a[i])
end
end
def to_s
#array.to_s
end
def transpose
size=vectors[0].length
arr= Array.new(size)
i=0
while i<size
a=Array.new(vector.length)
j=0
while j<a.length
a[j]=vectors[j].arr[i]
j+=1
end
arr[i]=a
i+=1
end
arr[i]=a
i+=1
end
def *m
if !(m instance_of? MyMatrix)
raise Error
a=Array.new(#array.length)
i=0
while (i<#array.length)
a[i]=#array[i]*m
i=i+1
end
end
end
end
Input:
Test code
v = MyVector.new([1,2,3])
puts "v = " + v.to_s
v1 = MyVector.new([2,3,4])
puts "v1 = " + v1.to_s
puts "v * v1 = " + (v * v1).to_s
m = MyMatrix.new([[1,2], [1, 2], [1, 2]])
puts "m = " + m.to_s + "\n"
puts "v * m = " + (v * m).to_s
m1 = MyMatrix.new([[1, 2, 3], [2, 3, 4]])
puts "m1 = " + m1.to_s + "\n"
puts "m * m1 = " + (m * m1).to_s
puts "m1 * m = " + (m1 * m).to_s
Desired Output:
v = 1 2 3
v1 = 2 3 4
v * v1 = 20
m =
1 2
1 2
1 2
v * m = 6 12
m1 =
1 2 3
2 3 4
m * m1 =
5 8 11
5 8 11
5 8 11
m1 * m =
6 12
9 18
To answer the infinite loop issue, it looks like you forgot to add a i += 1 in the #initialize method of Matrix class.
However, you will encounter more errors further in the code since, for example, you're checking length of the Matrix object which is undefined, and iterating over the Matrix object in each2 defined inside of the Vector class which needs the object to be an Enumerable (Array/Hash etc). These will throw an error as the Matrix class is not an Enumerator. These are some good resources to help you learn how the powerful Enumerator module works.
Once you get familiar with the syntax and structure, be sure to use the Pry tool. It will be your best friend for debugging Ruby code.
I'm asked to write the ruby program that generate the output based the given command,
The full description
I'm really new in ruby (maybe few hours that I have started ruby)
I'm getting this error, please check my code for other possible errors:
Thank you.
n `block in each2': undefined method `[]' for #<MyVector:0x00000002c4ad90 #array=[2, 3, 4]> (NoMethodError)
What I have done so far:
# MyVector Class
class MyVector
def initialize (a)
if !(a.instance_of? Array)
raise "ARGUMENT OF INITIALIZER MUST BE AN ARRAY"
else
#array = a
end
end
def array
#array
end
def to_s
#array.to_s
end
def length
#array.length
end
def each2(a)
raise Error, "INTEGER IS NOT LIKE VECTOR" if a.kind_of?(Integer)
Vector.Raise Error if length != a.length
return to_enum(:each2, a) unless block_given?
length.times do |i|
yield #array[i], a[i]
end
self
end
def * (a)
Vector.Raise Error if length != a.length
p = 0
each2(a) {|a1, a2|p += a1 * a2}
p
end
end
# MyMatrix Class
class MyMatrix
def initialize a
#array=Array.new(a.length)
i=0
while(i<a.length)
#array[i]=MyVector.new(a[i])
end
end
def to_s
#array.to_s
end
def transpose
size=vectors[0].length
arr= Array.new(size)
i=0
while i<size
a=Array.new(vector.length)
j=0
while j<a.length
a[j]=vectors[j].arr[i]
j+=1
end
arr[i]=a
i+=1
end
arr[i]=a
i+=1
end
def *m
if !(m instance_of? MyMatrix)
raise Error
a=Array.new(#array.length)
i=0
while (i<#array.length)
a[i]=#array[i]*m
i=i+1
end
end
end
end
Input:
Test code
v = MyVector.new([1,2,3])
puts "v = " + v.to_s
v1 = MyVector.new([2,3,4])
puts "v1 = " + v1.to_s
puts "v * v1 = " + (v * v1).to_s
m = MyMatrix.new([[1,2], [1, 2], [1, 2]])
puts "m = " + m.to_s + "\n"
puts "v * m = " + (v * m).to_s
m1 = MyMatrix.new([[1, 2, 3], [2, 3, 4]])
puts "m1 = " + m1.to_s + "\n"
puts "m * m1 = " + (m * m1).to_s
puts "m1 * m = " + (m1 * m).to_s
Desired Output:
v = 1 2 3
v1 = 2 3 4
v * v1 = 20
m =
1 2
1 2
1 2
v * m = 6 12
m1 =
1 2 3
2 3 4
m * m1 =
5 8 11
5 8 11
5 8 11
m1 * m =
6 12
9 18
length.times do |i|
yield #array[i], a[i]
end
In the above block, a is an instance of MyVector. You need to define the [] operator on it, probably something like:
def [](i)
#array[i]
end