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8287178: IntegerModuloP::multiplicativeInverse returns 0 for 0

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Reviewed-by: jnimeh
This commit is contained in:
Weijun Wang 2022-06-10 22:25:18 +00:00
parent da2339cf69
commit d4b473d890
1 changed files with 8 additions and 1 deletions
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9
src/java.base/share/classes/sun/security/util/math/IntegerModuloP.java
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@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2018, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -156,6 +156,13 @@ public interface IntegerModuloP {
* @return the multiplicative inverse (1 / this) * @return the multiplicative inverse (1 / this)
*/ */
default ImmutableIntegerModuloP multiplicativeInverse() { default ImmutableIntegerModuloP multiplicativeInverse() {
// This method is used in 2 cases:
// 1. To calculate the inverse of a number in ECDSAOperations,
// this number must be non zero (modulo p).
// 2. To flatten a 3D point to a 2D AffinePoint. This number
// might be zero (infinity). However, since the infinity
// is represented as (0, 0) in 2D, it’s OK returning 0 as
// the inverse of 0, i.e. (1, 1, 0) == (1/0, 1/0) == (0, 0).
return pow(getField().getSize().subtract(BigInteger.valueOf(2))); return pow(getField().getSize().subtract(BigInteger.valueOf(2)));
} }