RSA Cipher 的大输入

Question

我生成了以下 Public 输入 Android。

 fun createCipher(): Cipher
    {
        val posKey = posPublicKey
        posKey.publicKey.modulus

        var spec = RSAPublicKeySpec(BigInteger(posPublicKey.publicKey.modulus), BigInteger(posPublicKey.publicKey.exponent))
        var fact = KeyFactory.getInstance(KeyProperties.KEY_ALGORITHM_RSA)

        publicKey = fact.generatePublic(spec)
        var cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding")
        cipher.init(Cipher.ENCRYPT_MODE, publicKey)
        return cipher
    }

我选择的RSA密钥大小是4096字节指数为 3 个字节，模数为 512 个字节

取模字节数组如下：

[-32, -28, -121, 32, 109, -82, 43, 115, 43, -117, 20, 35, 122, 33, -2, 23, 23, -22, 75 , 0, 91, 10, -89, 48, 33, -89, 57, 1, 57, -13, 9, -127, 90, 121, -96, -94, 106, -16, -105, - 112, -74, 30, -12, 74, -74, 104, -26, 15, 99, -22, -55, -75, 14, -45, 56, 20, 85, 90, 83, -50 , 68, -114, 5, -10, -109, 79, 44, 81, 68, -98, -45, -51, -97, 71, 90, -13, -78, 118, -21, - 47、66、104、-83、56、-72、-27、45、16、70、32、-76、-125、-11、108、126、-61、-126、16、6、-49 , -106, -114, 18, 49, 121, -39, -109, 115, 111, -128, 83, 8, -110, -10, -4, 51, -67, 49, 66, 103, -76, -88, -110, 122, 56, 29, -101, 22, 3, 117, -104, -54, -64, -71, 23, 58, 87, 37, 96, 25, -114 , 38, 1, -126, 33, -91, -4, 89, -28, 10, 95, -104, -24, -38, 17, 47, -122, 24, -89, 123, 100, 12, -10, -57, -44, 45, 25, 39, -80, -101, -6, -99, -95, -5, 70, 32, 37, -57, -52, -47, -66, 85, 10, -48, 75, 4, -114, 104, -7, -112, -128, 4, 114, 77, -40, 96, 66, 83, -54, 10, 111, 102, -39, -63, 2, -75, 38, 36, 24, 13, -51, 96, 89, -60, -40, 99, 6 5, 123, 52, -114, 122, 75, 32, -121, 80, -76, -11, -1, -31, -118, -51, -21, 13, 109, 111, -102, 120, -56, 62, -19, -79, 86, -41, -81, 67, -80, -63, 37, 35, 47, 109, -32, 47, -128, 95, -48, -53, -1, -125, -19, -9, -10, 15, -116, -50, 53, -86, -102, -24, 107, 122, -43, -125, 51, 14 , 101, 67, 57, 116, 97, -40, -98, -82, -118, -83, 120, -107, -14, 19, -49, -27, 10, 25, 40, 43, -27、31、59、-57、58、33、-98、1、-45、-118、76、-21、-13、-123、67、42、-37、-96、-32、33 , 124, 1, 44, -99, 74, 18, 32, 10, -107, -121, 86, -115, -70, -107, 109, 17, -92, 109, -47, 60, - 49, -91, 7, -125, 47, 78, 86, 81, -2, -35, 17, 124, 94, -26, -80, -84, 120, 110, 38, -55, -90 , -11, 107, 73, 71, 44, 69, -58, 56, -59, 2, 94, 27, 88, 29, -57, 95, -99, 5, 102, -66, 118, - 82、126、20、-104、-95、47、-2、77、-33、89、-66、-92、121、-5、78、68、-1、-82、-95、-121 , 117, -29, 70, 11, -72, 54, -99, -13, -87, 9, 77, -113, 51, -124, -56, -8, 126, -114, -31, 90, -125, -11, 41, -85, 74, 3, 90, -95, 85, 121, 61, 14, 116, 51, -4 0, -57, -124, -69, -51, -76, -119, -80, 95, 95, 17, -34, 80, -36, 66, -51, 14, -69, -113, 35, -109, -115, -16, -3, -118, 114, -20, -81, 57, -65, 40, -8, -67, -85, 110, 50, -128, 44, -78, 93, -44, -93, 89, -76, 13, 98, -38, -55, -120, 11, 127, 84, -2, 101, 57, -121, -111, 91, -102, -118, 85, -124, -90, 91, -84, 28, 120, -28, -105, 88, -73, 6, 89, 33, 8, 9, 30, 9, -6 , 17, 25]

指数字节数组如下：

[1, 0, 1]

测试Key如下：

val stringKey = "8D-F7-5B-15-0F-2A-E5-3E-FD-44-5A-63-50-AC-62-D6-06-2D-59-5C-F1-C3-9A-DB-45-25-0D-7A-72-AE-DF-87"
val stringIV = "FA-94-FD-74-2E-AC-2C-90-79-98-AF-A3-D7-12-5D-A2"

 var aeskey = AesKeyBuilder()
            val key = (stringKey.replace("-", "")).toByteArray(Charsets.US_ASCII)

            val iv = (stringIV.replace("-", "")).toByteArray(Charsets.US_ASCII)
            aeskey.key = key
            aeskey.iv = iv

val encryptedKey = cipher.doFinal(aesKey.Key)

我要加密的项目是 64 字节。使用此 public 键。

但是，我收到以下错误：

Process: com.touchsides.rewards.debug, PID: 19470
com.android.org.bouncycastle.crypto.DataLengthException: input too large for RSA cipher.
    at com.android.org.bouncycastle.crypto.engines.RSACoreEngine.convertInput(RSACoreEngine.java:115)
    at com.android.org.bouncycastle.crypto.engines.RSABlindedEngine.processBlock(RSABlindedEngine.java:95)
    at com.android.org.bouncycastle.crypto.encodings.OAEPEncoding.encodeBlock(OAEPEncoding.java:199)
    at com.android.org.bouncycastle.crypto.encodings.OAEPEncoding.processBlock(OAEPEncoding.java:131)

我相信模数大小足以允许加密此字节数组。

Answer 1

您收到 com.android.org.bouncycastle.crypto.DataLengthException 错误，因为 RSA 密钥是使用负模数创建的。所以它不能用来加密一个字节。

BigInteger 默认构造函数使用提供的字节数组有效负载的最高有效位作为数字的符号位。所以你必须使用另一个构造函数明确指定你想要一个正数，其中第一个参数是一个符号指示符：

BigInteger(1, posPublicKey.publicKey.modulus), BigInteger(1, posPublicKey.publicKey.exponent)

还有一种 C# 方法可以在字节数组前面添加一个 zero-byte（因此符号位将始终为零）：

BigInteger(byteArrayOf(0) + posPublicKey.publicKey.modulus), BigInteger(byteArrayOf(0) + posPublicKey.publicKey.exponent)

最后，如果您的 BigInteger 创建方式有误，可以进行转换：

var modulus = BigInteger(posPublicKey.publicKey.modulus)
if (modulus.compareTo(BigInteger.ZERO) < 0)
    modulus = modulus.add(BigInteger.ONE.shiftLeft(4096))

请同时查看 and answers of this question。

RSA Cipher 的大输入

Input to large for RSA Cipher

java

android

rsa

public-key-encryption