JavaScript DHTML/Security/RSA Encoding
RSA Encoding in JavaScript
<source lang="html4strict">
<html>
<head>
<title>RSA Encoding</title>
</head>
<body>
<script language="JavaScript">0) {
r+=s.charAt(rand(sl))
}
//status("rstring "+r)
return r
} function key2(k) {
var l=k.length
var kl=l
var r=""
while(l--) {
r+=k.charAt((l*3)%kl)
}
return r
} function rsaEncrypt(keylen,key,mod,text) {
// I read that rc4 with keys larger than 256 bytes doesn"t significantly
// increase the level of rc4 encryption because it"s sbuffer is 256 bytes
// makes sense to me, but what do i know...
status("encrypt")
if(text.length >= keylen) {
var sessionkey=rc4(rstring(text,keylen),rstring(text,keylen))
// session key must be less than mod, so mod it
sessionkey=b2t(bmod(t2b(sessionkey),t2b(mod)))
alert("sessionkey="+sessionkey)
// return the rsa encoded key and the encrypted text
// i"m double encrypting because it would seem to me to
// lessen known-plaintext attacks, but what do i know
return modexp(sessionkey,key,mod) +
rc4(key2(sessionkey),rc4(sessionkey,text))
} else {
// don"t need a session key
return modexp(text,key,mod)
}
} function rsaDecrypt(keylen,key,mod,text) {
status("decrypt")
if(text.length <= keylen) {
return modexp(text,key,mod)
} else {
// sessionkey is first keylen bytes
var sessionkey=text.substr(0,keylen)
text=text.substr(keylen)
// un-rsa the session key
sessionkey=modexp(sessionkey,key,mod)
alert("sessionkey="+sessionkey)
// double decrypt the text
return rc4(sessionkey,rc4(key2(sessionkey,text),text))
}
} function trim2(d) { return d.substr(0,d.lastIndexOf("1")+1) } function bgcd(u,v) { // return greatest common divisor
// algorythm from http://algo.inria.fr/banderier/Seminar/Vallee/index.html var d, t while(1) { d=bsub(v,u) //alert(v+" - "+u+" = "+d) if(d=="0") {return u} if(d) { if(d.substr(-1)=="0") { v=d.substr(0,d.lastIndexOf("1")+1) // v=(v-u)/2^val2(v-u) } else v=d } else { t=v; v=u; u=t // swap u and v } }
} function isPrime(p) {
var n,p1,p12,t
p1=bsub(p,"1")
t=p1.length-p1.lastIndexOf("1")
p12=trim2(p1)
for(n=0; n<2; n+=mrtest(p,p1,p12,t)) {
if(n<0) return 0
}
return 1
} function mrtest(p,p1,p12,t) {
// Miller-Rabin test from forum.swathmore.edu/dr.math/
var n,a,u
a="1"+rstring("01",Math.floor(p.length/2)) // random a
//alert("mrtest "+p+", "+p1+", "+a+"-"+p12)
u=bmodexp(a,p12,p)
if(u=="1") {return 1}
for(n=0;n<t;n++) {
u=bmod(bmul(u,u),p)
//dg+=u+" "
if(u=="1") return -100
if(u==p1) return 1
}
return -100
} pfactors="11100011001110101111000110001101"
// this number is 3*5*7*11*13*17*19*23*29*31*37
function prime(bits) {
// return a prime number of bits length
var p="1"+rstring("001",bits-2)+"1"
while( ! isPrime(p)) {
p=badd(p,"10"); // add 2
}
alert("p is "+p)
return p
} function genkey(bits) {
q=prime(bits)
do {
p=q
q=prime(bits)
} while(bgcd(p,q)!="1")
p1q1=bmul(bsub(p,"1"),bsub(q,"1"))
// now we need a d, e, and an n so that:
// p1q1*n-1=de -> bmod(bsub(bmul(d,e),"1"),p1q1)="0"
// or more specifically an n so that d & p1q1 are rel prime and factor e
n="1"+rstring("001",Math.floor(bits/3)+2)
alert("n is "+n)
factorMe=badd(bmul(p1q1,n),"1")
alert("factor is "+factorMe)
//e=bgcd(factorMe,p1q1)
//alert("bgcd="+e)
e="1"
// is this always 1?
//r=bdiv(factorMe,e)
//alert("r="+r.q+" "+r.mod)
//if(r.mod != "0") {alert("Mod Error!")}
//factorMe=r.q
d=bgcd(factorMe,"11100011001110101111000110001101")
alert("d="+d)
if(d == "1" && e == "1") {alert("Factoring failed "+factorMe+" p="+p+" q="+q)}
e=bmul(e,d)
r=bdiv(factorMe,d)
d=r.q
if(r.mod != "0") {alert("Mod Error 2!")}
this.mod=b2t(bmul(p,q))
this.pub=b2t(e)
this.priv=b2t(d)
} function status(a) { }//alert(a)} // -->
</script>
RSA-type:
Note that long keys will likely be slow.<form method="POST" name="RSA">
| keylength: | <input type="text" size="4" name="keylen" value="2"> How many bytes? | |
| key: | <input type="text" size="60" name="key" value="10001"> | Binary |
|
modulo: |
<input type="text" size="60" name="mod" value="110010100001"> | Binary |
| text: | <textarea name="text" rows="6" cols="60"></textarea> | For sample values you can use:Public Key: 10001Private Key: 101011000001 |
<script language="JavaScript"></script> |
<input type="button" name="B1" value="Encrypt" onclick="RSAencryptDemo()"> <input type="button" name="B2" value="Decrypt" onclick="RSAdecryptDemo()"> |
</form> </body>
</html>
</source>