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package sun.security.rsa;

import java.security.*;

This class implements the MGF1 mask generation function defined in PKCS#1 v2.2 B.2.1 (https://tools.ietf.org/html/rfc8017#appendix-B.2.1). A mask generation function takes an octet string of variable length and a desired output length as input and outputs an octet string of the desired length. MGF1 is a mask generation function based on a hash function, i.e. message digest algorithm.
Since: 11
/** * This class implements the MGF1 mask generation function defined in PKCS#1 * v2.2 B.2.1 (https://tools.ietf.org/html/rfc8017#appendix-B.2.1). A mask * generation function takes an octet string of variable length and a * desired output length as input and outputs an octet string of the * desired length. MGF1 is a mask generation function based on a hash * function, i.e. message digest algorithm. * * @since 11 */
public final class MGF1 { private final MessageDigest md;
Construct an instance of MGF1 based on the specified digest algorithm.
/** * Construct an instance of MGF1 based on the specified digest algorithm. */
MGF1(String mdAlgo) throws NoSuchAlgorithmException { this.md = MessageDigest.getInstance(mdAlgo); }
Using the specified seed bytes, generate the mask, xor the mask with the specified output buffer and store the result into the output buffer (essentially replaced in place).
Params:
  • seed – the buffer holding the seed bytes
  • seedOfs – the index of the seed bytes
  • seedLen – the length of the seed bytes to be used by MGF1
  • maskLen – the intended length of the generated mask
  • out – the output buffer holding the mask
  • outOfs – the index of the output buffer for the mask
/** * Using the specified seed bytes, generate the mask, xor the mask * with the specified output buffer and store the result into the * output buffer (essentially replaced in place). * * @param seed the buffer holding the seed bytes * @param seedOfs the index of the seed bytes * @param seedLen the length of the seed bytes to be used by MGF1 * @param maskLen the intended length of the generated mask * @param out the output buffer holding the mask * @param outOfs the index of the output buffer for the mask */
void generateAndXor(byte[] seed, int seedOfs, int seedLen, int maskLen, byte[] out, int outOfs) throws RuntimeException { byte[] C = new byte[4]; // 32 bit counter byte[] digest = new byte[md.getDigestLength()]; while (maskLen > 0) { md.update(seed, seedOfs, seedLen); md.update(C); try { md.digest(digest, 0, digest.length); } catch (DigestException e) { // should never happen throw new RuntimeException(e.toString()); } for (int i = 0; (i < digest.length) && (maskLen > 0); maskLen--) { out[outOfs++] ^= digest[i++]; } if (maskLen > 0) { // increment counter for (int i = C.length - 1; (++C[i] == 0) && (i > 0); i--) { // empty } } } }
Returns the name of this MGF1 instance, i.e. "MGF1" followed by the digest algorithm it based on.
/** * Returns the name of this MGF1 instance, i.e. "MGF1" followed by the * digest algorithm it based on. */
String getName() { return "MGF1" + md.getAlgorithm(); } }