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今天模拟一个安卓程序的数据包，有一个sign_code参数，32位是个md5，简单把其他参数按经验组合后取md5，对不上，算了，直接看源代码吧

还好，代码混淆的很轻，dex2jar之后 搜索sign_code ，很快找到关键方法，跟之前猜的差不多，只是参数加密的顺序不一致，另外多了一个固定的字符串，就是防猜测的吧，呵呵

按照代码 在易语言里 对组合后的字符串取数据摘要 得到md5，发现竟然跟java里得到的md5值不一样。。。

仔细检查了一下反编译的java源码，发现其中用于取MD5的文本是UTF-8编码：

MessageDigest md = MessageDigest.getInstance("MD5");			md.update(plainText.getBytes("UTF-8"));			byte b[] = md.digest();

于是，解决方案也就很简单了，在易语言里先将字符串转为UTF-8,再取md5：

取数据摘要 (编码转换 (到字节集 (“我错了”), #编码_GB2312, #编码_UTF_8, ret))

字符串编码不同，可能会导致md5不同，这问题是在任何语言中都需要注意的，php，或者javascript里也是。这里再贴一个utf-8编码的取md5.js代码：

//计算MD5算法    var hexcase = 0;    function hex_md5(a) {        if (a == "") return a;        return rstr2hex(rstr_md5(str2rstr_utf8(a)));    }    function hex_hmac_md5(a, b) {        return rstr2hex(rstr_hmac_md5(str2rstr_utf8(a), str2rstr_utf8(b)));    }    function md5_vm_test() {        return hex_md5("abc").toLowerCase() == "900150983cd24fb0d6963f7d28e17f72";    }    function rstr_md5(a) {        return binl2rstr(binl_md5(rstr2binl(a), a.length * 8));    }    function rstr_hmac_md5(c, f) {        var e = rstr2binl(c);        if (e.length > 16) {            e = binl_md5(e, c.length * 8);        }        var a = Array(16), d = Array(16);        for (var b = 0; b < 16; b++) {            a[b] = e[b] ^ 909522486;            d[b] = e[b] ^ 1549556828;        }        var g = binl_md5(a.concat(rstr2binl(f)), 512 + f.length * 8);        return binl2rstr(binl_md5(d.concat(g), 512 + 128));    }    function rstr2hex(c) {        try {            hexcase;        } catch (g) {            hexcase = 0;        }        var f = hexcase ? "0123456789ABCDEF" :"0123456789abcdef";        var b = "";        var a;        for (var d = 0; d < c.length; d++) {            a = c.charCodeAt(d);            b += f.charAt(a >>> 4 & 15) + f.charAt(a & 15);        }        return b;    }    function str2rstr_utf8(c) {        var b = "";        var d = -1;        var a, e;        while (++d < c.length) {            a = c.charCodeAt(d);            e = d + 1 < c.length ? c.charCodeAt(d + 1) :0;            if (55296 <= a && a <= 56319 && 56320 <= e && e <= 57343) {                a = 65536 + ((a & 1023) << 10) + (e & 1023);                d++;            }            if (a <= 127) {                b += String.fromCharCode(a);            } else {                if (a <= 2047) {                    b += String.fromCharCode(192 | a >>> 6 & 31, 128 | a & 63);                } else {                    if (a <= 65535) {                        b += String.fromCharCode(224 | a >>> 12 & 15, 128 | a >>> 6 & 63, 128 | a & 63);                    } else {                        if (a <= 2097151) {                            b += String.fromCharCode(240 | a >>> 18 & 7, 128 | a >>> 12 & 63, 128 | a >>> 6 & 63, 128 | a & 63);                        }                    }                }            }        }        return b;    }    function rstr2binl(b) {        var a = Array(b.length >> 2);        for (var c = 0; c < a.length; c++) {            a[c] = 0;        }        for (var c = 0; c < b.length * 8; c += 8) {            a[c >> 5] |= (b.charCodeAt(c / 8) & 255) << c % 32;        }        return a;    }    function binl2rstr(b) {        var a = "";        for (var c = 0; c < b.length * 32; c += 8) {            a += String.fromCharCode(b[c >> 5] >>> c % 32 & 255);        }        return a;    }    function binl_md5(p, k) {        p[k >> 5] |= 128 << k % 32;        p[(k + 64 >>> 9 << 4) + 14] = k;        var o = 1732584193;        var n = -271733879;        var m = -1732584194;        var l = 271733878;        for (var g = 0; g < p.length; g += 16) {            var j = o;            var h = n;            var f = m;            var e = l;            o = md5_ff(o, n, m, l, p[g + 0], 7, -680876936);            l = md5_ff(l, o, n, m, p[g + 1], 12, -389564586);            m = md5_ff(m, l, o, n, p[g + 2], 17, 606105819);            n = md5_ff(n, m, l, o, p[g + 3], 22, -1044525330);            o = md5_ff(o, n, m, l, p[g + 4], 7, -176418897);            l = md5_ff(l, o, n, m, p[g + 5], 12, 1200080426);            m = md5_ff(m, l, o, n, p[g + 6], 17, -1473231341);            n = md5_ff(n, m, l, o, p[g + 7], 22, -45705983);            o = md5_ff(o, n, m, l, p[g + 8], 7, 1770035416);            l = md5_ff(l, o, n, m, p[g + 9], 12, -1958414417);            m = md5_ff(m, l, o, n, p[g + 10], 17, -42063);            n = md5_ff(n, m, l, o, p[g + 11], 22, -1990404162);            o = md5_ff(o, n, m, l, p[g + 12], 7, 1804603682);            l = md5_ff(l, o, n, m, p[g + 13], 12, -40341101);            m = md5_ff(m, l, o, n, p[g + 14], 17, -1502002290);            n = md5_ff(n, m, l, o, p[g + 15], 22, 1236535329);            o = md5_gg(o, n, m, l, p[g + 1], 5, -165796510);            l = md5_gg(l, o, n, m, p[g + 6], 9, -1069501632);            m = md5_gg(m, l, o, n, p[g + 11], 14, 643717713);            n = md5_gg(n, m, l, o, p[g + 0], 20, -373897302);            o = md5_gg(o, n, m, l, p[g + 5], 5, -701558691);            l = md5_gg(l, o, n, m, p[g + 10], 9, 38016083);            m = md5_gg(m, l, o, n, p[g + 15], 14, -660478335);            n = md5_gg(n, m, l, o, p[g + 4], 20, -405537848);            o = md5_gg(o, n, m, l, p[g + 9], 5, 568446438);            l = md5_gg(l, o, n, m, p[g + 14], 9, -1019803690);            m = md5_gg(m, l, o, n, p[g + 3], 14, -187363961);            n = md5_gg(n, m, l, o, p[g + 8], 20, 1163531501);            o = md5_gg(o, n, m, l, p[g + 13], 5, -1444681467);            l = md5_gg(l, o, n, m, p[g + 2], 9, -51403784);            m = md5_gg(m, l, o, n, p[g + 7], 14, 1735328473);            n = md5_gg(n, m, l, o, p[g + 12], 20, -1926607734);            o = md5_hh(o, n, m, l, p[g + 5], 4, -378558);            l = md5_hh(l, o, n, m, p[g + 8], 11, -2022574463);            m = md5_hh(m, l, o, n, p[g + 11], 16, 1839030562);            n = md5_hh(n, m, l, o, p[g + 14], 23, -35309556);            o = md5_hh(o, n, m, l, p[g + 1], 4, -1530992060);            l = md5_hh(l, o, n, m, p[g + 4], 11, 1272893353);            m = md5_hh(m, l, o, n, p[g + 7], 16, -155497632);            n = md5_hh(n, m, l, o, p[g + 10], 23, -1094730640);            o = md5_hh(o, n, m, l, p[g + 13], 4, 681279174);            l = md5_hh(l, o, n, m, p[g + 0], 11, -358537222);            m = md5_hh(m, l, o, n, p[g + 3], 16, -722521979);            n = md5_hh(n, m, l, o, p[g + 6], 23, 76029189);            o = md5_hh(o, n, m, l, p[g + 9], 4, -640364487);            l = md5_hh(l, o, n, m, p[g + 12], 11, -421815835);            m = md5_hh(m, l, o, n, p[g + 15], 16, 530742520);            n = md5_hh(n, m, l, o, p[g + 2], 23, -995338651);            o = md5_ii(o, n, m, l, p[g + 0], 6, -198630844);            l = md5_ii(l, o, n, m, p[g + 7], 10, 1126891415);            m = md5_ii(m, l, o, n, p[g + 14], 15, -1416354905);            n = md5_ii(n, m, l, o, p[g + 5], 21, -57434055);            o = md5_ii(o, n, m, l, p[g + 12], 6, 1700485571);            l = md5_ii(l, o, n, m, p[g + 3], 10, -1894986606);            m = md5_ii(m, l, o, n, p[g + 10], 15, -1051523);            n = md5_ii(n, m, l, o, p[g + 1], 21, -2054922799);            o = md5_ii(o, n, m, l, p[g + 8], 6, 1873313359);            l = md5_ii(l, o, n, m, p[g + 15], 10, -30611744);            m = md5_ii(m, l, o, n, p[g + 6], 15, -1560198380);            n = md5_ii(n, m, l, o, p[g + 13], 21, 1309151649);            o = md5_ii(o, n, m, l, p[g + 4], 6, -145523070);            l = md5_ii(l, o, n, m, p[g + 11], 10, -1120210379);            m = md5_ii(m, l, o, n, p[g + 2], 15, 718787259);            n = md5_ii(n, m, l, o, p[g + 9], 21, -343485551);            o = safe_add(o, j);            n = safe_add(n, h);            m = safe_add(m, f);            l = safe_add(l, e);        }        return Array(o, n, m, l);    }    function md5_cmn(h, e, d, c, g, f) {        return safe_add(bit_rol(safe_add(safe_add(e, h), safe_add(c, f)), g), d);    }    function md5_ff(g, f, k, j, e, i, h) {        return md5_cmn(f & k | ~f & j, g, f, e, i, h);    }    function md5_gg(g, f, k, j, e, i, h) {        return md5_cmn(f & j | k & ~j, g, f, e, i, h);    }    function md5_hh(g, f, k, j, e, i, h) {        return md5_cmn(f ^ k ^ j, g, f, e, i, h);    }    function md5_ii(g, f, k, j, e, i, h) {        return md5_cmn(k ^ (f | ~j), g, f, e, i, h);    }    function safe_add(a, d) {        var c = (a & 65535) + (d & 65535);        var b = (a >> 16) + (d >> 16) + (c >> 16);        return b << 16 | c & 65535;    }    function bit_rol(a, b) {        return a << b | a >>> 32 - b;    }

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