简单加密算术库（SEAL）和seal :: Ciphertext变量 [英] Simple Encrypted Arithmetic Library (SEAL) and the seal::Ciphertext variable

问题描述

我正在使用简单加密算术Microsoft密码研究小组的Library（SEAL）库。有没有办法获取 seal :: Ciphertext变量的内容？我试图了解ciphertext.h和ciphertext.cpp并找到了：

I'm using the Simple Encrypted Arithmetic Library (SEAL) library from Microsoft Cryptography Research Group. Is there a way to get the content of seal::Ciphertext variable? I've tried to understand the ciphertext.h and ciphertext.cpp and found the:

/**
Saves the ciphertext to an output stream. The output is in binary format and not 
human-readable. The output stream must have the "binary" flag set.

@param[in] stream The stream to save the ciphertext to
@see load() to load a saved ciphertext.
*/
void save(std::ostream &stream) const;

/**
Loads a ciphertext from an input stream overwriting the current ciphertext.

@param[in] stream The stream to load the ciphertext from
@see save() to save a ciphertext.
*/
void load(std::istream &stream);

但我找不到其他方法来获取任何密封件的内容:: Ciphertext变量不是二进制流，也不是指向某个内存地址的指针，而是将其保存为字符串。

But I coudn't find another option to get the content of anyseal::Ciphertext variable that is not a binary stream or just a pointer to some memory address and save it a string.

如果有人从上面的链接下载了SEAL库并提取了它，而没有进行任何更改。您可以在 SEAL_2.3.1\SEAL\seal\ciphertext.h 和中的 seal :: Ciphertext 上找到所有允许的操作> SEAL_2.3.1\SEAL\seal\ciphertext.cpp

If any of you have download the SEAL library from the link above and extracted it without changing anything. You can find all the allowed operations on seal::Ciphertext in SEAL_2.3.1\SEAL\seal\ciphertext.h and SEAL_2.3.1\SEAL\seal\ciphertext.cpp

推荐答案

简短的答案是：没有其他方法可以在SEAL中访问密文数据。 Ciphertext :: data 返回的指针将使您可以直接访问密文数据，从这种意义上讲，您可以对其进行任何类型的计算，例如

Short answer is that there are no other ways of accessing the ciphertext data in SEAL. The pointer returned by Ciphertext::data will give you direct access to the ciphertext data and in that sense allows you to do any kind of computation on it, e.g. converting to a human-readable string if for some reason you would want to do that.

当然，要执行任何可理解的操作，您需要了解密文的数据布局。在BFV方案中，密文由一对多项式（c ₀ ，c ₁ ）组成，其大小较大（ coeff_modulus ）系数。由于对具有如此大系数的多项式进行运算很不方便，因此SEAL 2.3.1改为使用复合 coeff_modulus 并存储c ₀ 和c ₁ 对 coeff_modulus 中指定的每个主要因子取模（表示这些因子q ₁ ，q ₂ ，...，q _k ）。每个q _i 都适合一个64位单词，因此所有这2k多项式都具有单词大小系数。

Of course to do anything intelligible you need to know the data layout of the ciphertext. In the BFV scheme a ciphertext consists of a pair of polynomials (c₀, c₁) with large (size coeff_modulus) coefficients. Since operating on polynomials with such large coefficients is inconvenient, SEAL 2.3.1 instead uses a composite coeff_modulus and stores both c₀ and c₁ modulo each of the prime factors specified in the coeff_modulus (denote these factors q₁,q₂,...,q_k). Each q_i fits into a 64-bit word, so all of these 2k polynomials have word-size coefficients.

密文系数数据布局如下（在内存中连续）：

The ciphertext coefficient data layout is as follows (contiguous in memory):

[c ₀ mod q ₁ ] [c ₀ mod q ₂ ] ... [c ₀ mod q _k ] [c ₁ mod q ₁ ] [c ₁ mod q ₂ ] ... [c ₁ mod q _k ]

[ c₀ mod q₁ ][ c₀ mod q₂ ]...[ c₀ mod q_k ][ c₁ mod q₁ ][ c₁ mod q₂ ]...[ c₁ mod q_k ]

其中每个[c _i mod q _j ]看起来像

where each [ c_i mod q_j ] looks like

[c ₀ [0] mod q _j ] [c ₁ [0] mod q _j ] ... [c _n-1 [0] mod q _j ]

[ c₀[0] mod q_j ][ c₁[0] mod q_j ]...[ c_n-1[0] mod q_j ]

在这里，我使用c _i [k]表示c _i 的度k系数。请注意，每个系数都存储在 uint64_t 中。

Here I used c_i[k] to denote the degree k coefficient of c_i. Note that each coefficient is stored in a uint64_t.

Ciphertext :: data 返回指向c ₀ 的常数系数的指针关于 coeff_modulus 中的第一个模的多项式，即c ₀ [0] mod q ₁ 。除此系数数据外，密文还包含其他一些可以使用成员函数读取的字段。

Ciphertext::data returns a pointer to the constant coefficient of the c₀ polynomial with respect to the first modulus in your coeff_modulus, i.e. to c₀[0] mod q₁. In addition to this coefficient data, a Ciphertext contains a few other fields that you can read using the member functions.

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