Understanding RSA key generation and implementation in Java

Here is an attempt to leverage Java's BigInteger class to implement the RSA algorithm, as well as md5 and sha512 hashing functions to generate keys for what I hope to be strong cryptography. My prayer is that some of my ideas are novel and not just wrong.

• This is a test, this is only a test. 'Keys' are generated, the message is encrypted, displayed, decrypted, displayed, and all tossed out with the bathwater.
• This implementation ignores salting. I suppose my thought here is that computational complexity (time) and memory requirements for a large enough key would dissuade an adversary from successfully utilizing a rainbow table.
• I understand using a sieve of Eratosthenes to pick out a value for e is overkill, expensive, and could be functionally reproduced here by taking a pseudo-random number and finding nextProbablePrime(). I've included it hoping to get feedback on this implementation.
• I am a total novice. I was a New Media major. I want to learn. I humbly request any time and thoughts you wish to impart. Running time is ~1m; half due to the sieve, half for the 1000 iterations of nextProbablyPrime().

RSATest.java: (Usage: java RSATest "some password" "some message")

import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class RSATest {
  //seive array for lower 2b primes
  public static byte[] a = new byte[(Integer.MAX_VALUE/20)+1];
  public static BigInteger p=BigInteger.ONE,q=BigInteger.ONE,t;
  public static MessageDigest sha,md5;
  public static int lp = 3; // last prime sieved
  //method returns prime number after hash with given digest
  public static BigInteger h(byte[] ba, MessageDigest md){
    BigInteger t=(new BigInteger(md.digest(ba))).abs().nextProbablePrime();
    md.update(t.toByteArray());
    return t;
  }
  public static void main(String[] args) {
    BigInteger e,n,t,d,sec,cy,dec;
    byte[] a,ar;
    String secret;
    int itr, itr2; //itr: iterations
    if(args.length!=2){
      System.out.println("HELP - parameters: \"password\" \"message\"");
      System.exit(1);
    }
    secret=args[1];
    //TODO: reject palindromes?
    a=args[0].getBytes();
    ar = (new StringBuilder(args[0])).reverse().toString().getBytes();
    //init sha and md5 digest methods with string
    try {
        sha = MessageDigest.getInstance("SHA-512");
        sha.update(a);
        md5 = MessageDigest.getInstance("MD5");
        md5.update(a);
    } catch (NoSuchAlgorithmException ex) {
        ex.printStackTrace();
        System.exit(0);
    }
    //generate primes from hash of string and its reverse
    p=p.multiply(h(a,sha)).nextProbablePrime();
    p=p.multiply(h(a,md5)).nextProbablePrime();
    p=p.multiply(h(ar,sha)).nextProbablePrime();
    p=p.multiply(h(ar,md5)).nextProbablePrime();
    sha.update(p.toByteArray());
    md5.update(p.toByteArray());
    q=q.multiply(h(ar,sha)).nextProbablePrime();
    q=q.multiply(h(ar,md5)).nextProbablePrime();
    sha.update(q.toByteArray());
    md5.update(q.toByteArray());
    q=q.multiply(h(a,sha)).nextProbablePrime();
    q=q.multiply(h(a,md5)).nextProbablePrime();
    //increase computational time and ensure primality of p/q
    itr = p.mod(BigInteger.valueOf(1000)).intValue();
    itr2 = 1000-itr;
    for(int i = 1;i<itr;i++)p=p.nextProbablePrime();
    for(int x = 1;x<itr2;x++)q=q.nextProbablePrime();
    while(!p.isProbablePrime(Integer.MAX_VALUE))p=p.nextProbablePrime();
    while(!q.isProbablePrime(Integer.MAX_VALUE))q=q.nextProbablePrime();
    System.out.println("P:"+p.toString(10));
    System.out.println("Q:"+q.toString(10));
    //for exponent
    //aquire one of the lower primes using sieve
    //pseudo random prime between 7 and int max
    si(p.mod(BigInteger.valueOf(Integer.MAX_VALUE)).intValue());
    e = BigInteger.valueOf(lp);
    //rsa encrypt and decrypt
    n = p.multiply(q);
    t = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));
    d = e.modInverse(t);
    sec = new BigInteger(secret.getBytes());
    //cypher text
    cy = sec.modPow(e,n);
    System.out.println("C:"+cy.toString(16));
    //decrypted text
    dec = cy.modPow(d,n);
    System.out.println("D:"+(new String(dec.toByteArray())));
  }
  //sieve of eratosthenes
  public static void si(int max){
    s(3);
    s(7);
    for(int i=11;i<max;i+=10){
      if(t(i))s(i);
      if(0<(i+2)&&t(i+2))s(i+2);
      if(0<(i+6)&&t(i+6))s(i+6);
      if(0<(i+8)&&t(i+8))s(i+8);
    }
  }
  //get test bit from sieve
  public static boolean t(int i){
    return (a[i/20]&b(i))==0;
  }
  //int value to bit mask used in sieve
  public static byte b(int i){
    return (byte)(1<<(((i%20)/2)-((i%20)/5)+((i%20)/10)));
  }
  //sieve forward prime value i
  public static void s(int i) {
    lp=i;for(int w=3*i;w>0;w+=(((w+i+i)%5)==0?4*i:2*i))a[w/20]|=b(w);
  }
}

Is there any value here? My ambition is to understand the computational and cryptographic theory and translate this into best practices. I apologize for the terrible naming of variables and methods, heinous runtime, useless commenting, unnecessary golfing, and using spaces over tabs.

Example output:

>java RSATest "password" "test"

P:10090275631957288744610599659040664305405434722352094636668421960416506099994666827664511624543986219997911864288607312795882978242921884901347541608283715814165727102775081158850275803219608306098677869589957898032998379673745817876752829320076809618549060139888917446177159027216418146574898873844039044426500320311838804799370581535223413777861948749552759092994514733751610983813
Q:5425365986445829161530505882662909832813406327751968505626162017780151029106074817664839063991268038579259781345806774068118642908105542837724653877104358137779083102271171002417267868641163457971958213047417570560412152250447538894719454784926316581576607321753609289397778946058304937920474724957098706683798464369444644490724812822892582670707683075052137846220273984681853710951
C: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
D:test