Substitution cipher

Question

A substitution cipher is an encoding method where each letter in the alphabet is replaced with a fixed, different one; for example, given the following substitution map:

abcdefghijklmnopqrstuvwxyz
            ||
qwertyuiopasdfghjklzxcvbnm

The phrase "we all love cryptography" would be encoded as "vt qss sgct eknhzgukqhin".

The program will continuously read its input, one line at time; the first line will contain the substitution map, in the form of all 26 letters, in any order, without repetitions, missing letters or extraneous characters; it will be interpreted as "the first letter is the substitution for A, the second letter is the substitution for B [...] the 26th letter is the substitution for Z"; no output will be provided after reading it. For each subsequent line, the program will output the encoded text corresponding to the line. Only letters will be encoded; numbers, symbols and whitespaces will be simply copied to the output.

For simplicity, all input (including the substitution map) will only contain lowercase characters.

Sample input:

qwertyuiopasdfghjklzxcvbnm
hello
bye!
i don't know.

Sample output:

itssg
wnt!
o rgf'z afgv.

As usual, the shortest solution wins.

---

Additional clarifications on input:

• The program must read its input stream (I thought that was clear); command line parameters, files, named pipes, network sockets, quantum entanglement or extra sensorial perceptions are not allowed.
• The input must include only the actual text to be processed; quotes, brackets, commas or any other symbol, if found, should simply be copied to the output as they are.
• No additional characters should be required in the input. If your program requires the input text to be placed in quotes, brackets, commas or any other delimiter, then You Are Doing It Wrong (TM).
• "Line" is defined as a string of characters followed by a newline; the actual implementation of "newline" if usually left to the OS, but if you need to go into its details, just use whatever you prefer.
• An empty line is no special case; the program could either print an empty line or do nothing, but it should not print any actual text, crash, exit, destroy the operating system, set fire to the house, collapse the Sun in a black hole, summon demons from other planes of existence or replace your toothpaste with mayonnaise.
• There is no requirement for the program to run interactively; it's free to suck all its input in and then print all its output; there is also not any time limit on its execution, although it would be definitely preferable for it to terminate before the heat death of the universe.

Answer 1

Convex, 4 6 5 bytes

_{Crossed out 4 is still regular 4 :(}

Note: As @Dennis pointed out, the input format I was using was not up to spec. This version should comply with the new rules, though.

lqT@Ë

Try it online

Explanation:

l       Read a line from input
 q      Read the rest of the input
  T     Push lowercase alphabet ("abcdefghijklmnopqrstuvwxyz")
   @    Rotate the top 3 items on the stack.
    er  Transliterate
        Implied output

Thanks to @LuisMendo for pointing out an error in the program

Answer 2

Pyth, 7 bytes

V.zXNGz

Try it online!

How it works:

V.zXNGz
        G = "abcdefghijklmnopqrstuvwxyz"
        z = input()
V.z     for N in all_input():
   XNGz     N.translate(G,z)    <--- automatically printed

Answer 3

JavaScript ES6, 65 62 49 bytes

Saved 2 bytes thanks to Neil.

(a,i)=>a.replace(/./g,x=>i[x.charCodeAt()-97]||x)

Takes an string of lines a and a dictionary i.

Answer 4

CJam, 12 8 bytes

4 bytes saved thanks to Dennis!

l_$q\@er

Try it online!

Explanation

l        e# read a line
_$       e# fancy way to obtain string "abc...z". Thanks to Dennis!
q        e# read the rest of input as a string with newlines
\@       e# swap, rotate
er       e# transliterate. Implicit display

Answer 5

sh + coreutils, 16 bytes

read s;tr a-z $s

15 bytes if input is from a terminal:

tr a-z `sed 1q`

Answer 6

05AB1E, 5 bytes

Code:

[A¹‡,

Explanation:

[      # Start an infinite loop.
 A     # Push the lowercase alphabet.
  ¹    # Push the first input (substitution map).
   ‡   # Transliterate. Since the arity of this function is 3 and there are only 2 values
                        on the stack, it implicitly takes a line of input.
    ,  # Pop and print.

So this continually reads a line of input and prints a line of input after. Uses CP-1252 encoding. This is what I got with the console version:

D:\Golfing\05AB1E>C:\Python34\python.exe 05AB1E.py test.abe
qwertyuiopasdfghjklzxcvbnm
hello
itssg
welcome
vtsegdt
greetings, planet!
ukttzoful, hsqftz!

Trying this online might be a bit weird, since 05AB1E is trying to read another line of input, but there is none, so you need to kill it to receive output (doesn't work all the time). It might be a better idea to do this with the console version of 05AB1E. Try it online!.

Answer 7

JavaScript 89

for(i=prompt,x=i(),n='';p=i();n+=p.replace(/./g,m=>x[m.charCodeAt(0)-97])+"\n");
alert(n)

Answer 8

Ruby, 35 31 29 bytes

Credit to @QPaysTaxes for the $_ trick, I had assumed that reading more from the STDIN object $< would change that variable, but it doesn't.

gets
$><<$<.read.tr('a-z',$_)

String#tr is basically a cipher substitution function, making things quite simple.

Answer 9

MATL, 14 bytes

jXKx`jHY2KXEDT

The program exits with an error after producing the correct output (allowed by default).

Try it online

Answer 10

Python 3, 50 bytes

lambda s,k:s.translate(dict(zip(range(97,122),k)))

Or if we really have to implement an infinite loop:

Python 3, 70 bytes

t=dict(zip(range(97,122),input()))
while 1:print(input().translate(t))

Answer 11

Pyth, 34 Bytes 31 Bytes 29 Bytes 27 Bytes

Saved 3 5 7 bytes thanks to Kenny Lau

jmsm?&<JCk123>J96@hQ-J97kdt

Try it out!

Answer 12

Factor, 155 bytes

The logic is actually pretty simple, it's just constraining to the REPL requirement that costs.

[let "abcdefghijklmnopqrstuvwxyz" readln string>array bi@ zip :> T [ t ] [ T readln string>array [ dup T key? [ T at ] [ ] if ] map "" join print ] while ]

Readable single-function version (don't ever write code like this):

:: monolithic-repl ( -- )
    "abcdefghijklmnopqrstuvwxyz" readln string>array bi@ zip 
  :> table
  [ t ] 
  [ table readln string>array
    [ dup table key? 
      [ table at ] [ ] if 
    ] map
    "" join print 
  ] while ;

Readable, Factored version:

:: cipher-print ( cipher-table -- )
  readln string>array
  [ dup cipher-table key? [ cipher-table at ] [ ] if ] map
  "" join print ;

: cipher-get ( -- cipher )
  "abcdefghijklmnopqrstuvwxyz" readln
  string>array bi@ zip ;

:: cipher-repl ( -- )
  cipher-get :> table
  [ t ] [ table cipher-print ] while ;

Answer 13

C++, 154 Bytes

#include <iostream.h>
#include "string.h"
using namespace std;

void encript_string() {
char en[26],in[1024];
string s=cin.getline();
strcpy(en,s.c_str());
while(1){
 s=cin.get_line();
 strcpy(in,s.c_str());
 int i=0,m=0;
 while(in[i] != 10) {
  m=in[i]-97;
  cout<<en[m];
 }
 cout<<"\n";
}
}