JS base64编码加解密、JS编码转换

关注

原创最新推荐文章于 2026-09-05 21:51:56 发布 697 阅读 AI 写同款· GEO 优化 ›

国密SM4前后端加解密实战：JavaScript与Java互通避坑指南本文深入剖析了国密SM4算法在JavaScript前端与Java后端加解密互通时常见的“坑”，如字符编码、字节数组转换、Base64处理等核心差异。通过提供经过验证的代码示例和系统性排查指南，旨在帮助开发者构建稳定、一致的跨语言SM4加解密方案，确保金融、政务等高安全要求场景的数据安全。阅读详情

len = str.length;

        i = 0;
        out = "";
        while (i < len) {

            do {
                c1 = base64decodechars[str.charCodeAt(i++) & 0xff];
            } while (i < len && c1 == -1);
            if (c1 == -1)
                break;

            do {
                c2 = base64decodechars[str.charCodeAt(i++) & 0xff];
            } while (i < len && c2 == -1);
            if (c2 == -1)
                break;

out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));

            do {
                c3 = str.charCodeAt(i++) & 0xff;
                if (c3 == 61)
                    return out;
                c3 = base64decodechars[c3];
            } while (i < len && c3 == -1);
            if (c3 == -1)
                break;

out += String.fromCharCode(((c2 & 0xf) << 4) | ((c3 & 0x3c) >> 2));

            do {
                c4 = str.charCodeAt(i++) & 0xff;
                if (c4 == 61)
                    return out;
                c4 = base64decodechars[c4];
            } while (i < len && c4 == -1);
            if (c4 == -1)
                break;
            out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
        }
        return out;
    }

    function utf8to16(str) {
        var out, i, len, c;
        var char2, char3;

        out = "";
        len = str.length;
        i = 0;
        while (i < len) {
            c = str.charCodeAt(i++);
            switch (c >> 4) {
                case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                    // 0xxxxxxx
                    out += str.charAt(i - 1);
                    break;
                case 12: case 13:
                    // 110x xxxx   10xx xxxx
                    char2 = str.charCodeAt(i++);
                    out += String.fromCharCode(((c & 0x1f) << 6) | (char2 & 0x3f));
                    break;
                case 14:
                    // 1110 xxxx 10xx xxxx 10xx xxxx
                    char2 = str.charCodeAt(i++);
                    char3 = str.charCodeAt(i++);
                    out += String.fromCharCode(((c & 0x0f) << 12) |
                       ((char2 & 0x3f) << 6) |
                       ((char3 & 0x3f) << 0));
                    break;
            }
        }

return out;
}

    function doit() {
        var f = document.f
        f.output.value = base64encode(utf16to8(f.source.value))
        f.decode.value = utf8to16(base64decode(f.output.value))
    }
</script>