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Diffstat (limited to 'libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/GF2nField.java')
| -rw-r--r-- | libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/GF2nField.java | 292 |
1 files changed, 0 insertions, 292 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/GF2nField.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/GF2nField.java deleted file mode 100644 index d1aa13633..000000000 --- a/libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/GF2nField.java +++ /dev/null @@ -1,292 +0,0 @@ -package org.spongycastle.pqc.math.linearalgebra; - - -import java.util.Vector; - - -/** - * This abstract class defines the finite field <i>GF(2<sup>n</sup>)</i>. It - * holds the extension degree <i>n</i>, the characteristic, the irreducible - * fieldpolynomial and conversion matrices. GF2nField is implemented by the - * classes GF2nPolynomialField and GF2nONBField. - * - * @see GF2nONBField - * @see GF2nPolynomialField - */ -public abstract class GF2nField -{ - - /** - * the degree of this field - */ - protected int mDegree; - - /** - * the irreducible fieldPolynomial stored in normal order (also for ONB) - */ - protected GF2Polynomial fieldPolynomial; - - /** - * holds a list of GF2nFields to which elements have been converted and thus - * a COB-Matrix exists - */ - protected Vector fields; - - /** - * the COB matrices - */ - protected Vector matrices; - - /** - * Returns the degree <i>n</i> of this field. - * - * @return the degree <i>n</i> of this field - */ - public final int getDegree() - { - return mDegree; - } - - /** - * Returns the fieldpolynomial as a new Bitstring. - * - * @return a copy of the fieldpolynomial as a new Bitstring - */ - public final GF2Polynomial getFieldPolynomial() - { - if (fieldPolynomial == null) - { - computeFieldPolynomial(); - } - return new GF2Polynomial(fieldPolynomial); - } - - /** - * Decides whether the given object <tt>other</tt> is the same as this - * field. - * - * @param other another object - * @return (this == other) - */ - public final boolean equals(Object other) - { - if (other == null || !(other instanceof GF2nField)) - { - return false; - } - - GF2nField otherField = (GF2nField)other; - - if (otherField.mDegree != mDegree) - { - return false; - } - if (!fieldPolynomial.equals(otherField.fieldPolynomial)) - { - return false; - } - if ((this instanceof GF2nPolynomialField) - && !(otherField instanceof GF2nPolynomialField)) - { - return false; - } - if ((this instanceof GF2nONBField) - && !(otherField instanceof GF2nONBField)) - { - return false; - } - return true; - } - - /** - * @return the hash code of this field - */ - public int hashCode() - { - return mDegree + fieldPolynomial.hashCode(); - } - - /** - * Computes a random root from the given irreducible fieldpolynomial - * according to IEEE 1363 algorithm A.5.6. This cal take very long for big - * degrees. - * - * @param B0FieldPolynomial the fieldpolynomial if the other basis as a Bitstring - * @return a random root of BOFieldPolynomial in representation according to - * this field - * @see "P1363 A.5.6, p103f" - */ - protected abstract GF2nElement getRandomRoot(GF2Polynomial B0FieldPolynomial); - - /** - * Computes the change-of-basis matrix for basis conversion according to - * 1363. The result is stored in the lists fields and matrices. - * - * @param B1 the GF2nField to convert to - * @see "P1363 A.7.3, p111ff" - */ - protected abstract void computeCOBMatrix(GF2nField B1); - - /** - * Computes the fieldpolynomial. This can take a long time for big degrees. - */ - protected abstract void computeFieldPolynomial(); - - /** - * Inverts the given matrix represented as bitstrings. - * - * @param matrix the matrix to invert as a Bitstring[] - * @return matrix^(-1) - */ - protected final GF2Polynomial[] invertMatrix(GF2Polynomial[] matrix) - { - GF2Polynomial[] a = new GF2Polynomial[matrix.length]; - GF2Polynomial[] inv = new GF2Polynomial[matrix.length]; - GF2Polynomial dummy; - int i, j; - // initialize a as a copy of matrix and inv as E(inheitsmatrix) - for (i = 0; i < mDegree; i++) - { - try - { - a[i] = new GF2Polynomial(matrix[i]); - inv[i] = new GF2Polynomial(mDegree); - inv[i].setBit(mDegree - 1 - i); - } - catch (RuntimeException BDNEExc) - { - BDNEExc.printStackTrace(); - } - } - // construct triangle matrix so that for each a[i] the first i bits are - // zero - for (i = 0; i < mDegree - 1; i++) - { - // find column where bit i is set - j = i; - while ((j < mDegree) && !a[j].testBit(mDegree - 1 - i)) - { - j++; - } - if (j >= mDegree) - { - throw new RuntimeException( - "GF2nField.invertMatrix: Matrix cannot be inverted!"); - } - if (i != j) - { // swap a[i]/a[j] and inv[i]/inv[j] - dummy = a[i]; - a[i] = a[j]; - a[j] = dummy; - dummy = inv[i]; - inv[i] = inv[j]; - inv[j] = dummy; - } - for (j = i + 1; j < mDegree; j++) - { // add column i to all columns>i - // having their i-th bit set - if (a[j].testBit(mDegree - 1 - i)) - { - a[j].addToThis(a[i]); - inv[j].addToThis(inv[i]); - } - } - } - // construct Einheitsmatrix from a - for (i = mDegree - 1; i > 0; i--) - { - for (j = i - 1; j >= 0; j--) - { // eliminate the i-th bit in all - // columns < i - if (a[j].testBit(mDegree - 1 - i)) - { - a[j].addToThis(a[i]); - inv[j].addToThis(inv[i]); - } - } - } - return inv; - } - - /** - * Converts the given element in representation according to this field to a - * new element in representation according to B1 using the change-of-basis - * matrix calculated by computeCOBMatrix. - * - * @param elem the GF2nElement to convert - * @param basis the basis to convert <tt>elem</tt> to - * @return <tt>elem</tt> converted to a new element representation - * according to <tt>basis</tt> - * @throws DifferentFieldsException if <tt>elem</tt> cannot be converted according to - * <tt>basis</tt>. - * @see GF2nField#computeCOBMatrix - * @see GF2nField#getRandomRoot - * @see GF2nPolynomial - * @see "P1363 A.7 p109ff" - */ - public final GF2nElement convert(GF2nElement elem, GF2nField basis) - throws RuntimeException - { - if (basis == this) - { - return (GF2nElement)elem.clone(); - } - if (fieldPolynomial.equals(basis.fieldPolynomial)) - { - return (GF2nElement)elem.clone(); - } - if (mDegree != basis.mDegree) - { - throw new RuntimeException("GF2nField.convert: B1 has a" - + " different degree and thus cannot be coverted to!"); - } - - int i; - GF2Polynomial[] COBMatrix; - i = fields.indexOf(basis); - if (i == -1) - { - computeCOBMatrix(basis); - i = fields.indexOf(basis); - } - COBMatrix = (GF2Polynomial[])matrices.elementAt(i); - - GF2nElement elemCopy = (GF2nElement)elem.clone(); - if (elemCopy instanceof GF2nONBElement) - { - // remember: ONB treats its bits in reverse order - ((GF2nONBElement)elemCopy).reverseOrder(); - } - GF2Polynomial bs = new GF2Polynomial(mDegree, elemCopy.toFlexiBigInt()); - bs.expandN(mDegree); - GF2Polynomial result = new GF2Polynomial(mDegree); - for (i = 0; i < mDegree; i++) - { - if (bs.vectorMult(COBMatrix[i])) - { - result.setBit(mDegree - 1 - i); - } - } - if (basis instanceof GF2nPolynomialField) - { - return new GF2nPolynomialElement((GF2nPolynomialField)basis, - result); - } - else if (basis instanceof GF2nONBField) - { - GF2nONBElement res = new GF2nONBElement((GF2nONBField)basis, - result.toFlexiBigInt()); - // TODO Remember: ONB treats its Bits in reverse order !!! - res.reverseOrder(); - return res; - } - else - { - throw new RuntimeException( - "GF2nField.convert: B1 must be an instance of " - + "GF2nPolynomialField or GF2nONBField!"); - } - - } - -} |