Vigenère cipher: Difference between revisions
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<lang j> 'VIGENERECIPHER' vigEncryptRC 'Beware the Jabberwock, my son! The jaws that bite, the claws that catch!' |
<lang j> 'VIGENERECIPHER' vigEncryptRC 'Beware the Jabberwock, my son! The jaws that bite, the claws that catch!' |
||
WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY |
WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY |
||
'VIGENERECIPHER' vigDecryptRC 'WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY' |
'VIGENERECIPHER' vigDecryptRC 'WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY' |
||
BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH</lang> |
BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH</lang> |
Revision as of 21:31, 31 May 2011
Implement a Vigenère cypher, both encryption and decryption. The program should handle keys and text of unequal length, and should capitalize everything and discard non-alphabetic characters. (If your program handles non-alphabetic characters in another way, make a note of it.)
See also:
ALGOL 68
Note: This specimen retains the original C++ coding style.
<lang algol68>STRING key := "";
PROC vigenere cipher = (REF STRING key)VOID: (
FOR i FROM LWB key TO UPB key DO IF key[i] >= "A" AND key[i] <= "Z" THEN key +:= key[i] FI; IF key[i] >= "a" AND key[i] <= "z" THEN key +:= REPR(ABS key[i] + ABS"A" - ABS"a") FI OD
);
PROC encrypt = (STRING text)STRING: (
STRING out := "";
INT j := LWB text; FOR i FROM LWB text TO UPB text DO CHAR c := text[i];
IF c >= "a" AND c <= "z" THEN c := REPR(ABS c + (ABS"A" - ABS"a")) FI; IF c >= "A" AND c <= "Z" THEN out +:= REPR((ABS c + ABS key[j] - 2*ABS"A") MOD 26 + ABS"A"); j := j MOD UPB key + 1 FI OD;
out
);
PROC decrypt = (STRING text)STRING: (
STRING out;
INT j := LWB text; FOR i FROM LWB text TO UPB text DO CHAR c := text[i];
IF c >= "a" AND c <= "z" THEN c := REPR(ABS c + (ABS"A" - ABS"a")) FI; IF c >= "A" AND c <= "Z" THEN out +:= REPR((ABS c - ABS key[j] + 26) MOD 26 + ABS"A"); j := j MOD UPB key + 1 FI OD;
out
);
main: (
vigenere cipher(key:="VIGENERECIPHER");
STRING original := "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!"; STRING encrypted := encrypt(original); STRING decrypted := decrypt(encrypted);
print((original, new line)); print(("Encrypted: ", encrypted, new line)); print(("Decrypted: ", decrypted, new line))
)</lang> Output:
Beware the Jabberwock, my son! The jaws that bite, the claws that catch! Encrypted: WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY Decrypted: BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH
C++
<lang cpp>#include <iostream>
- include <string>
using namespace std;
class Vigenere { public:
string key;
Vigenere(string key) { for(int i = 0; i < key.size(); ++i) { if(key[i] >= 'A' && key[i] <= 'Z') this->key += key[i]; else if(key[i] >= 'a' && key[i] <= 'z') this->key += key[i] + 'A' - 'a'; } }
string encrypt(string text) { string out;
for(int i = 0, j = 0; i < text.length(); ++i) { char c = text[i]; if(c >= 'a' && c <= 'z') c += 'A' - 'a'; else if(c < 'A' || c > 'Z') continue;
out += (c + key[j] - 2*'A') % 26 + 'A'; j = (j + 1) % key.length(); }
return out; }
string decrypt(string text) { string out;
for(int i = 0, j = 0; i < text.length(); ++i) { char c = text[i]; if(c >= 'a' && c <= 'z') c += 'A' - 'a'; else if(c < 'A' || c > 'Z') continue;
out += (c - key[j] + 26) % 26 + 'A'; j = (j + 1) % key.length(); }
return out; }
};
int main() {
Vigenere cipher("VIGENERECIPHER");
string original = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!"; string encrypted = cipher.encrypt(original); string decrypted = cipher.decrypt(encrypted);
cout << original << endl; cout << "Encrypted: " << encrypted << endl; cout << "Decrypted: " << decrypted << endl;
}</lang>
Output:
Beware the Jabberwock, my son! The jaws that bite, the claws that catch! Encrypted: WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY Decrypted: BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH
Icon and Unicon
<lang Icon>procedure main()
ptext := "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!" write("Key = ",ekey := "VIGENERECIPHER") write("Plain Text = ",ptext) write("Normalized = ",GFormat(ptext := NormalizeText(ptext))) write("Enciphered = ",GFormat(ctext := Vignere("e",ekey,ptext))) write("Deciphered = ",GFormat(ptext := Vignere("d",ekey,ctext)))
end
procedure Vignere(mode,ekey,ptext,alpha) #: Vignere cipher
/alpha := &ucase # default if *alpha ~= *cset(alpha) then runerr(205,alpha) # no dups alpha ||:= alpha # unobstructed
every ctext:="" & p:=ptext[i := 1 to *ptext] & k:=ekey[(i-1)%*ekey+1] do case mode of { "e"|"encrypt": ctext||:=map(p,alpha[1+:*alpha/2],alpha[find(k,alpha)+:(*alpha/2)]) "d"|"decrypt": ctext||:=map(p,alpha[find(k,alpha)+:(*alpha/2)],alpha[1+:*alpha/2]) default: runerr(205,mode) }
return ctext end</lang>
The following helper procedures will be of general use with classical cryptography tasks. <lang Icon> link strings
procedure NormalizeText(ptext,alpha) #: text/case classical crypto helper
/alpha := &ucase # default if &lcase === (alpha := cset(alpha)) then ptext := map(ptext) # lower if &ucase === alpha then ptext := map(ptext,&lcase,&ucase) # upper return deletec(ptext,&cset--alpha) # only alphas
end
procedure GFormat(text) #: 5 letter group formatting helper
text ? (s := "", until pos(0) do s ||:= " " || move(5)|tab(0)) return s[2:0]
end</lang>
Output:
Key = VIGENERECIPHER Plain Text = Beware the Jabberwock, my son! The jaws that bite, the claws that catch! Normalized = BEWAR ETHEJ ABBER WOCKM YSONT HEJAW STHAT BITET HECLA WSTHA TCATCH Enciphered = WMCEE IKLGR PIFVM EUGXQ PWQVI OIAVE YXUEK FKBTA LVXTG AFXYE VKPAGY Deciphered = BEWAR ETHEJ ABBER WOCKM YSONT HEJAW STHAT BITET HECLA WSTHA TCATCH
J
Solution:
Using vig
from the convert/misc/vig addon:
<lang j>NB.*vig c Vigenère cipher
NB. cipher=. key 0 vig charset plain
NB. plain=. key 1 vig charset cipher
vig=: conjunction define
r=. (#y) $ n i.x n {~ (#n) | (r*_1^m) + n i.y
)
ALPHA=: (65,:26) ];.0 a. NB. Character Set preprocess=: (#~ e.&ALPHA)@toupper NB. force uppercase and discard non-alpha chars vigEncryptRC=: 0 vig ALPHA preprocess vigDecryptRC=: 1 vig ALPHA preprocess</lang>
Example Use: <lang j> 'VIGENERECIPHER' vigEncryptRC 'Beware the Jabberwock, my son! The jaws that bite, the claws that catch!' WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY
'VIGENERECIPHER' vigDecryptRC 'WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY'
BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH</lang>