Some XSLT templates that can convert Hex to Base64, for some reason.

hexToBase64.xslt

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" encoding="ascii" indent="yes" omit-xml-declaration="yes"/>
    <xsl:template match="Hex">
        <xsl:call-template name="bin2b64">
            <xsl:with-param name="x">
                <xsl:call-template name="hex2bin">
                    <xsl:with-param name="x" select="text()"/>
                </xsl:call-template>
            </xsl:with-param>
        </xsl:call-template>
    </xsl:template>
    <xsl:template name="bin2b64">
        <xsl:param name="x" select="."/>
        <xsl:variable name="b64" select="substring($x,1,1)*32+substring($x,2,1)*16+substring($x,3,1)*8+substring($x,4,1)*4+substring($x,5,1)*2+substring($x,6,1)"/>
        <xsl:value-of select="substring('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/',$b64+1,1)"/>
        <xsl:choose>
            <xsl:when test="string-length($x) > 6">
                <xsl:call-template name="bin2b64">
                    <xsl:with-param name="x" select="substring($x,7)"/>
                </xsl:call-template>
            </xsl:when>
            <xsl:otherwise>
                <xsl:value-of select="substring('==',1,(6-string-length($x)) div 2)"/>
            </xsl:otherwise>
        </xsl:choose>
    </xsl:template>
    <xsl:template name="hex2bin">
        <Binary>
            <xsl:call-template name="hex2bin_text">
                <xsl:with-param name="x" select="text()"/>
            </xsl:call-template>
        </Binary>
    </xsl:template>
    <xsl:template name="hex2bin_text">
        <xsl:param name="x" select="."/>
        <xsl:variable name="hex" select="substring($x,1,1)"/>
        <xsl:variable name="dec" select="string-length(substring-before('0123456789ABCDEF',translate($hex,'abcdef','ABCDEF')))"/>
        <xsl:value-of select="floor($dec div 8) mod 2"/>
        <xsl:value-of select="floor($dec div 4) mod 2"/>
        <xsl:value-of select="floor($dec div 2) mod 2"/>
        <xsl:value-of select="$dec mod 2"/>
        <xsl:if test="string-length($x) > 1">
            <xsl:call-template name="hex2bin_text">
                <xsl:with-param name="x" select="substring($x,2)"/>
            </xsl:call-template>
        </xsl:if>
    </xsl:template>
</xsl:stylesheet>