Re: Encrypt a number
Angelo Chen wrote:
angelo
On Mar 25, 10:22 am, Arne Vajh?j <a...@vajhoej.dk> wrote:
Angelo Chen wrote:
On Mar 25, 9:35 am, Arne Vajh?j <a...@vajhoej.dk> wrote:
angelochen...@gmail.com wrote:
I'm looking for a way to encrypt a number into an alpha string, the
result should be:
1) reversible
2) same or less size of the original, say: given 123456789, result
might be: asbQqzW
Any idea how to achieve this?
How secure should it be ?
A lot of the standard encryption algorithms may increase
size due to rounding length up to multipla of block size.
If obfuscation is good enough then:
public static String enc(String s) {
return Integer.toString(Integer.parseInt(s, 10), 36);
}
public static String dec(String s) {
return Integer.toString(Integer.parseInt(s, 36), 10);
}
> Thanks, this meets my need, but is there a way that I can specify a
> table, say,
> 0123456789abcdefghijklmnpqrstuvwxyzWXYZ
See below for some quickly written code.
private static String DIGITS =
"0123456789abcdefghijklmnpqrstuvwxyzWXYZ";
private static int fromAny(String s, int radix) {
int res = 0;
char[] sa = s.toCharArray();
int sign = 1;
for (int i = 0; i < s.length(); i++) {
if(sa[i] != '-') {
res = res * radix + DIGITS.indexOf(sa[i]);
} else {
sign = -1;
}
}
return sign * res;
}
private static String toAny(int i, int radix) {
if(i >= 0) {
String res = "";
int tmp = i;
while (tmp > 0) {
res = DIGITS.toCharArray()[tmp % radix] + res;
tmp = tmp / radix;
}
return res;
} else {
return "-" + toAny(-i, radix);
}
}
public static String enc(String s) {
return toAny(fromAny(s, 10), 36);
}
public static String dec(String s) {
return toAny(fromAny(s, 36), 10);
}
That's fast, I tested the code and it works, since enc/dec accepts
string, is it possible to have leading zeros, say '0526871', then when
reverse the encoded string, it can go back to '0526871' instead of
'526871'?
private static String DIGITS =
"0123456789abcdefghijklmnpqrstuvwxyzWXYZ";
private static int fromAny(String s, int radix, int[] z) {
int res = 0;
char[] sa = s.toCharArray();
int sign = 1;
boolean fz = true;
for (int i = 0; i < s.length(); i++) {
if(fz && sa[i] == '0') {
z[0]++;
} else if(sa[i] != '-') {
res = res * radix + DIGITS.indexOf(sa[i]);
fz = false;
} else {
sign = -1;
}
}
return sign * res;
}
private static String toAny(int i, int radix, int[] z) {
if(i >= 0) {
String res = "";
int tmp = i;
while (tmp > 0) {
res = DIGITS.toCharArray()[tmp % radix] + res;
tmp = tmp / radix;
}
for(int k = 0; k < z[0]; k++) res = '0' + res;
return res;
} else {
return "-" + toAny(-i, radix, z);
}
}
public static String enc(String s) {
int[] z = new int[1];
return toAny(fromAny(s, 10, z), 36, z);
}
public static String dec(String s) {
int[] z = new int[1];
return toAny(fromAny(s, 36, z), 10, z);
}
Arne