Understand an algorithm to find a prime of bit length $k$












1












$begingroup$


My cryptography notes gives this algorithm for finding a prime of bit-length larger than or equal to $k$.




  1. Determine an optimal bound on the set of small primes to be sieved
    $(2,3,...,p_t)$ and let $M=(2)(3)...p_t$.

  2. Generate a random integer $x$ whose bitlength is $k$ and locate, using the Chinese Remainder theorem, the smallest integer $x_1$ larger than $x$ which is co-prime to $M$.

  3. Perform an incremental search for primes in the set $x_1, x_1+M, x_1+2M$.


I have two questions




  1. How do you find the smallest integer $x_1>x$ using the Chinese remainder theorem that is co-prime to $M$.


  2. Why is it true that any of the integers in $(x_1, x_1+M$) are sieved. How do we know none of them are primes?



Thanks.










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$endgroup$

















    1












    $begingroup$


    My cryptography notes gives this algorithm for finding a prime of bit-length larger than or equal to $k$.




    1. Determine an optimal bound on the set of small primes to be sieved
      $(2,3,...,p_t)$ and let $M=(2)(3)...p_t$.

    2. Generate a random integer $x$ whose bitlength is $k$ and locate, using the Chinese Remainder theorem, the smallest integer $x_1$ larger than $x$ which is co-prime to $M$.

    3. Perform an incremental search for primes in the set $x_1, x_1+M, x_1+2M$.


    I have two questions




    1. How do you find the smallest integer $x_1>x$ using the Chinese remainder theorem that is co-prime to $M$.


    2. Why is it true that any of the integers in $(x_1, x_1+M$) are sieved. How do we know none of them are primes?



    Thanks.










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      My cryptography notes gives this algorithm for finding a prime of bit-length larger than or equal to $k$.




      1. Determine an optimal bound on the set of small primes to be sieved
        $(2,3,...,p_t)$ and let $M=(2)(3)...p_t$.

      2. Generate a random integer $x$ whose bitlength is $k$ and locate, using the Chinese Remainder theorem, the smallest integer $x_1$ larger than $x$ which is co-prime to $M$.

      3. Perform an incremental search for primes in the set $x_1, x_1+M, x_1+2M$.


      I have two questions




      1. How do you find the smallest integer $x_1>x$ using the Chinese remainder theorem that is co-prime to $M$.


      2. Why is it true that any of the integers in $(x_1, x_1+M$) are sieved. How do we know none of them are primes?



      Thanks.










      share|cite|improve this question









      $endgroup$




      My cryptography notes gives this algorithm for finding a prime of bit-length larger than or equal to $k$.




      1. Determine an optimal bound on the set of small primes to be sieved
        $(2,3,...,p_t)$ and let $M=(2)(3)...p_t$.

      2. Generate a random integer $x$ whose bitlength is $k$ and locate, using the Chinese Remainder theorem, the smallest integer $x_1$ larger than $x$ which is co-prime to $M$.

      3. Perform an incremental search for primes in the set $x_1, x_1+M, x_1+2M$.


      I have two questions




      1. How do you find the smallest integer $x_1>x$ using the Chinese remainder theorem that is co-prime to $M$.


      2. Why is it true that any of the integers in $(x_1, x_1+M$) are sieved. How do we know none of them are primes?



      Thanks.







      cryptography






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      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 26 at 22:07









      IntegrateThisIntegrateThis

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