Package org.mariadb.jdbc.internal.com.send.authentication.ed25519.math.ed25519

Class ScalarOps

java.lang.Object

org.mariadb.jdbc.internal.com.send.authentication.ed25519.math.ed25519.ScalarOps

public class ScalarOps
extends Object

Class for reducing a huge integer modulo the group order q and doing a combined multiply plus add plus reduce operation.

$q = 2^{252} + 27742317777372353535851937790883648493$.

Reviewed/commented by Bloody Rookie ([email protected])

Constructor Summary

Constructors

Constructor	Description
ScalarOps()

Method Summary

Modifier and Type	Method	Description
byte[]	multiplyAndAdd(byte[] a, byte[] b, byte[] c)	$(ab+c) \bmod q$
byte[]	reduce(byte[] s)	Reduction modulo the group order $q$.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ScalarOps

public ScalarOps()

Method Detail

reduce

public byte[] reduce(byte[] s)

Reduction modulo the group order $q$.

Input: $s[0]+256*s[1]+\dots+256^{63}*s[63] = s$

Output: $s[0]+256*s[1]+\dots+256^{31}*s[31] = s \bmod q$ where $q = 2^{252} + 27742317777372353535851937790883648493$.

Parameters:

s - byte array

Returns:

reduced byte array using a huge integer modulo the group order q

multiplyAndAdd

public byte[] multiplyAndAdd(byte[] a,
                             byte[] b,
                             byte[] c)

$(ab+c) \bmod q$

Input:

• $a[0]+256*a[1]+\dots+256^{31}*a[31] = a$
• $b[0]+256*b[1]+\dots+256^{31}*b[31] = b$
• $c[0]+256*c[1]+\dots+256^{31}*c[31] = c$

Output: $result[0]+256*result[1]+\dots+256^{31}*result[31] = (ab+c) \bmod q$ where $q = 2^{252} + 27742317777372353535851937790883648493$.

See the comments in reduce(byte[]) for an explanation of the algorithm.

Parameters:

a - a

b - b

c - c

Returns:

multiplied result