A blockchain-based transaction-amount-based covert communication method and system

Abstract

The present application relates to the technical field of covert communication, and particularly relates to a blockchain covert communication method and system based on transaction amount, which comprises the following steps: a seed key is negotiated by a message sender and a message receiver, the seed key is expanded into an amount embedding key and a shared address sequence by using a key expansion algorithm; the message sender embeds a message into a transaction amount, specifically including: encrypting private information and converting it into a binary stream, and converting the amount embedding key into a binary stream; the encrypted secret message binary stream is embedded into the transaction amount based on the amount embedding key binary stream, and a transaction is constructed through a blockchain for broadcasting; the message receiver extracts a transaction containing a covert message from the blockchain according to the address sequence, sorts and reorganizes the transaction, obtains the transaction amount, extracts the covert message from the transaction amount, and decrypts the private information; the present application is simple to implement, and has good concealment and security.

Description

Technical Field

[0001] This invention relates to the field of covert communication technology, and in particular to a blockchain covert communication method and system based on transaction amount. Background Technology

[0002] Covert channels aim to protect the relationship between sender and receiver by concealing the existence of clandestine communications, providing reliable privacy in sensitive scenarios. There are two main types of covert channels: Covert Timed Channels (CTC) and Covert Stored Channels (CSCs). CTCs hide covert information in timed behavior and are significantly affected by network latency or jitter; therefore, they are less robust. CSCs hide covert messages in stored fields, can be detected by pattern classification, and can be tampered with through normalization. A practical covert channel requires robustness, reliability, resistance to attribution, and undetectability. With the continuous improvement of traffic analysis, traditional covert channels can no longer fully meet these requirements, thus necessitating new methods for covert communication.

[0003] Blockchain networks are free for participants to join and use digital accounts instead of real-world identities to provide user anonymity. Furthermore, the flooding mechanism ensures that transactions can always be transmitted from sender to receiver without direct communication. These open, anonymous, and tamper-resistant characteristics make blockchain a natural channel for building covert channels.

[0004] Current blockchain covert communication solutions require the recipient to deploy a blockchain node within the network to cyclically scan all transactions and identify covert communication transactions. However, due to the massive number of blockchain transactions, scanning all transactions from each block is inefficient, and the recipient cannot access the confidential information using a mobile phone. Therefore, to address the issues of complex implementation and low efficiency in identifying covert communication transactions in existing solutions, a new covert communication solution is urgently needed that improves the efficiency of covert communication transaction identification while ensuring security, and is simple to implement and usable on mobile phones. Summary of the Invention

[0005] In view of this, the present invention proposes a blockchain covert communication method based on transaction amount, specifically including:

[0006] The message sender and receiver jointly negotiate a seed key, and then use a key expansion algorithm to expand the seed key into an amount embedding key. and share a set of address sequences;

[0007] The message sender embeds the message into the transaction amount, specifically including:

[0008] The private information is encrypted and converted into a binary stream, with the amount embedded in the key. Convert to binary stream ;

[0009] The binary stream of the secret message is embedded into the transaction amount based on the amount embedding key, and the transaction is carried out through the blockchain;

[0010] The message receiver retrieves transactions containing covert information based on the shared address sequence, sorts the transactions, obtains the transaction amount, and extracts the covert message from the transaction amount.

[0011] Furthermore, the process of embedding the encrypted binary stream of the secret message into the transaction amount based on the amount embedding key includes:

[0012] The first 8 digits of the transaction amount are used for message embedding, corresponding to the binary stream. The data is divided into slices, each slice being 8 bits.

[0013] Determine each binary stream Find the corresponding decimal value and determine whether the value is parity.

[0014] Each bit of the transaction amount is associated with a binary stream. Each bit is mapped to another, if the binary stream If a corresponding bit is 1, it indicates that the message is valid.

[0015] If valid, then embed it into the binary stream at that bit. If the corresponding decimal values ​​are the same (odd or even), then embed them into the binary stream. The corresponding decimal values ​​of numbers with different parity;

[0016] If binary stream If a corresponding bit is 0, it means that the message in that bit is invalid. A number is randomly selected as the bit for that position based on the frequency of the amount in the actual transaction.

[0017] Select the next shard key and repeat the above steps until all private messages are embedded into the transaction amount.

[0018] Furthermore, the process by which the message recipient extracts hidden messages from the transaction amount includes:

[0019] The message receiver collects transactions containing secret messages from the blockchain based on a shared address sequence, sorts the transactions according to the address sequence, and extracts the transaction amount of each transaction in turn.

[0020] Embedded key for amount Divide the data into segments, each segment consisting of eight digits, and sequentially correspond these segments to the eight decimal places of each amount.

[0021] The current key value of 1 indicates that the corresponding bit is valid. If the current bit is valid and the parity of the decimal corresponding to the current chip key is the same as the parity of the corresponding transaction amount, then the value of this bit in the secret message is 1; otherwise, the value of this bit in the secret message is 0.

[0022] The current key value is 0, indicating that the corresponding bit is invalid. Continue calculating the next bit.

[0023] This invention also proposes a blockchain covert communication system based on transaction amount, used to implement a blockchain covert communication method based on transaction amount, including a sharing module, a message encryption module, a binary stream conversion module, a secret message embedding module, a blockchain transaction module, a covert transaction identification module, a decoding module, a character conversion module, and a message decryption module, wherein:

[0024] The sharing module is used to negotiate the seed key and shared address sequence between the message sender and the message receiver;

[0025] The message encryption module is used to encrypt secret information;

[0026] The binary stream conversion module is used to embed the encrypted secret message and amount into the key. Convert to a binary stream;

[0027] The secret message embedding module is used to embed a binary stream of a secret message into the transaction amount based on the amount embedding key.

[0028] The blockchain transaction module is used to construct and send blockchain transactions. It selects the address sequence and the amount generated in the secret message embedding module in sequence to construct and send the blockchain transaction.

[0029] The covert transaction identification module is used to identify blocks containing secret messages based on transaction addresses and sort them according to addresses;

[0030] The decoding module is used to decode the transaction amount and obtain the binary stream of the secret message;

[0031] The character conversion module is used to convert binary streams into characters;

[0032] The message decryption module is used to decrypt characters into plaintext messages.

[0033] The covert communication method of this invention is essentially a transfer operation from the sender to a shared address sequence. The receiver only needs to find the transaction based on the shared address, reassemble the transaction according to the address sequence, and then recover the secret information based on the transfer amount and the shared seed key. Compared with the prior art, this invention has significant advantages in the following aspects:

[0034] 1. Simple to implement and deploy: Neither the sender nor the receiver needs to deploy network nodes. After constructing the covert communication transaction amount, the sender can use a third-party platform to send the transaction normally to the address in the address sequence. The receiver can download covert communication transaction extraction software on their mobile phone. The extraction software is linked to the API interface of the third-party query platform. Simply import the shared address sequence into the extraction software, and the software will automatically query transactions related to the address sequence on the third-party platform. Then, it will reconstruct all transactions locally based on the address sequence and recover the secret information based on the transaction amount and the shared seed key.

[0035] 2. Excellent security, which is reflected in the following aspects: (1) Covert communication transactions are no different from ordinary transfer transactions in the blockchain network, and are therefore unidentifiable. Moreover, the recipient uses address sequence to receive covert communication transactions, which can resist address association attacks while ensuring the orderliness of transactions, and further improves the concealment; (2) The covert channel of this invention is built on the blockchain, so its robustness, untraceability and anti-traceability can be well guaranteed. Attached Figure Description

[0036] Figure 1 This is the blockchain covert communication model based on transaction amount described in this invention;

[0037] Figure 2 This is an example flow diagram of a specific embodiment of the present invention;

[0038] Figure 3 This is a flowchart illustrating how the present invention embeds a binary stream of a secret message, encrypted using a key embedded in the amount, into the transaction amount.

[0039] Figure 4 This is a flowchart illustrating how the message receiver extracts hidden messages from the transaction amount in this invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] This invention proposes a blockchain covert communication method based on transaction amount, specifically including:

[0042] The message sender and receiver jointly negotiate a seed key, and then use a key expansion algorithm to expand the seed key into an amount embedding key. and share the address sequence;

[0043] The message sender embeds the message into the transaction amount, specifically including:

[0044] The private information is encrypted and converted into a binary stream, with the amount embedded in the key. Convert to binary stream ;

[0045] The binary stream of the secret message is embedded into the transaction amount based on the amount embedding key, and the transaction is carried out through the blockchain;

[0046] The message recipient obtains the transaction amount and extracts hidden messages from it.

[0047] In this embodiment, a blockchain covert communication method based on transaction amount includes three sub-processes: pre-negotiation, message embedding, and message extraction.

[0048] (a) Prior consultation

[0049] Step 1: Both communicating parties agree on a seed key and use a key expansion algorithm to expand the seed key into a message encryption key. and amount embedded key and share a sufficiently long address sequence;

[0050] Step 2: The sender uses the key Encrypt private messages that need to be communicated using AES to obtain the ciphertext message. ;

[0051] Step 3: The sender embeds the amount into the key. With ciphertext All are converted to binary streams, i.e. , Indicates will Convert to a binary stream.

[0052] (ii) Message embedding

[0053] Step 1: Embed the amount into the binary key The key is sharded into 8-bit segments. Each bit in the key segment corresponds to a decimal place of the blockchain transaction amount. The parity of the decimal number corresponding to each segment is determined. If the decimal number is odd, the parity of that segment key is odd, and vice versa. The parity of each segment key is thus obtained.

[0054] Step 2: Construct the covert communication transaction amount by sequentially fragmenting the keys. This bit being '1' indicates that it is a valid bit used for embedding the message. The parity of the fragment key pair controls whether the decimal part of the amount in the corresponding position is odd or even. The specific rule is: if the fragment key is even, and the message is binary... If the value is '1', the decimal position of the corresponding bit is embedded with an even number, while if the message is binary... If the value is '0', an odd number is embedded in the decimal position of the corresponding amount. The opposite applies if the sharding key is odd.

[0055] like If this bit is '0', it is a invalid bit, and the amount is randomly selected based on the frequency of this bit's occurrence in actual transactions. Therefore, each key binary corresponds to a transaction amount, and each amount contains a portion of the encrypted message's binary stream.

[0056] Step 3: Repeat step 2 using the next key binary fragment to embed the encrypted message into the transaction amount until all messages are fully embedded, thus obtaining all the covert communication amounts;

[0057] Step 4: The sender constructs the transaction normally, changes the amount of each transaction to the amount of the covert communication transaction in sequence, takes the addresses in the address sequence as the transaction receiving addresses, and sends the covert communication transaction to the receiver.

[0058] The following example illustrates the process of embedding secret messages into transaction amounts based on a key, specifically including the following steps:

[0059] If the fragmentation key is 01001101, the ciphertext binary is '1001';

[0060] This key fragment can embed 4 bits of information, namely the 2nd, 5th, 6th and 8th bits of the decimal part of the amount are valid bits, representing secret information;

[0061] The key is 115 in decimal, meaning the parity of the fragment key is odd. The secret information '1001' is embedded sequentially in the valid part. Then, the second decimal place of the amount is randomly selected as an odd number 5, the fifth decimal place is randomly selected as an even number 2, the sixth decimal place is randomly selected as an even number 6, and the eighth decimal place is randomly selected as an odd number 3. The other non-valid parts are selected according to the frequency of their occurrence in the actual transaction. Finally, the amount of the covert communication transaction is 0.15382633.

[0062] (III) Message Extraction

[0063] Step 1: The receiver checks transactions whose received addresses are address sequences, identifies covert communication transactions, and reassembles the transactions according to the address sequence;

[0064] Step 2: Convert to binary stream to obtain The data is divided into 8-bit segments, and the parity of the corresponding decimal number for each segment is determined.

[0065] Step 3: Extract the transaction amount of all covert communication transactions, and sequentially select the fragmentation key. Based on the valid bits of the fragmentation key and the embedding rules, obtain the ciphertext of the message embedded in the transaction amount.

[0066] Step 4: Repeat Step 3 to obtain the binary stream of ciphertext information embedded in all covert communication transaction amounts, and concatenate them to obtain... ;

[0067] Step 5: Perform the reverse operation z on the ciphertext binary stream, and the receiver obtains the encrypted secret information. ,Right now: Then use the key Perform AES decryption to obtain the final plaintext message.

[0068] This embodiment provides a specific process for obtaining a secret message based on the transaction amount and key decoding, including the following steps:

[0069] The recipient knows the transaction amount is 0.15382633, and the fragmentation key is 01001101.

[0070] The decimal value of the fragmentation key is 115, indicating that the parity of the fragmentation key is odd.

[0071] Check the valid bits in the fragment key, which are bits 2, 5, 6, and 8.

[0072] Checking the 2nd, 5th, 6th, and 8th decimal places of the transaction amount, the 2nd place is odd, and the parity of the fragmentation key is also odd, which means that the encrypted message '1' is embedded. The 5th place is even, and the parity of the fragmentation key is odd, which means that the encrypted message '0' is embedded. The same applies to the 6th and 8th places. Finally, we can obtain the ciphertext of the message embedded in the transaction amount of this covert communication as '1001'.

[0073] The following embodiment uses the sending of the secret message "test" as an example to further illustrate the present invention, so as to make the technical content clearer and easier to understand. The described embodiment is only a representative embodiment of the present invention, and not all embodiments. All embodiments based on the present invention fall within the protection scope of the present invention.

[0074] This invention uses a legitimate digital currency test network, and the detailed process is as follows: Figure 2 As shown, the specific implementation method of the sender is described below:

[0075] Step 1: Both communicating parties agree on a seed key and use a key expansion algorithm to expand the seed key message into an encryption key. Embedded key with amount and share a sufficiently long sequence of blockchain addresses;

[0076] Step 2: The sender uses The message is encrypted, and the encrypted message and amount are embedded with the key and converted into binary streams. With key binary and data encryption key As shown in Table 1;

[0077] Step 3: Based on the message binary and the fragment key binary To construct the covert communication transaction amount, 15 transactions are ultimately required, with transaction amounts of: 0.32817315, 0.38952326, 0.45264238...0.11632591, 0.156;

[0078] Step 4: The sender transfers funds sequentially to addresses in the shared address sequence, with the transfer amount being the amount of the covert communication transaction.

[0079] Table 1 Key and Binary Related Information

[0080] Cy5KRxWa1acmw7wKkUp3H4 / h5ouXu2DwGbXDA6qisTQ= 0110110001000010010010110110011101010011001100010110011100111101 0100100101110011110010011011110111000110111101001100110000110100111010110101100011101101110110001110000100110111011110101011011110101011010011010101001001110001001110101111001011000011011100111101101000001111010101110011011001111110000111010010001100011001

[0081] To better protect confidential messages, they can be encrypted before being converted into a binary stream. In this embodiment, the encryption key can be shared while both parties negotiate the seed key. The encrypted binary data message is then embedded, such as... Figure 1 The encrypted secret message is converted into a binary stream. Then based on the binary key Embed the amount, such as Figure 2 Specifically, it includes:

[0082] According to the binary key shown in Table 1, the key is divided into eight-bit segments. The first segment is "01001001". This segment has three valid bits "1", meaning that the second, fifth, and eighth bits can all be used to embed secret messages. The first segment can be used to embed the first three bits of the secret message "011" in sequence.

[0083] The first key "01001001" corresponds to the decimal value 73, which is an odd number. Therefore, the second digit is embedded with an even number, the fifth digit with an odd number, the eighth digit with an odd number, and the other digits are filled according to their frequency of occurrence.

[0084] In this embodiment, the result after filling is 0.32817315.

[0085] like Figure 2 In this embodiment, the message is binary. Embedded within 15 transactions, each transaction corresponds to an address. For example, the first transaction with a value of "0.32817315" corresponds to the address "mcfkvRpXEdubtXVojC6w4kUoxtT2crZuon". This address is the first in the shared address sequence between the message sender and the message receiver.

[0086] For the remaining address sequence and transaction amount, the transactions are processed sequentially from 1 to n. The message receiver can obtain the correct arrangement of the corresponding transaction amount by sorting the transactions according to the addresses from 1 to n.

[0087] Since each address sequence has a certain order number, the message sender sends secret messages in the order of the address sequence, and the message receiver arranges the received sequences in order.

[0088] The specific implementation method of the receiver is described as follows:

[0089] Step 1: The receiver identifies all covert communication transactions whose receiving addresses are address sequences, reorders all transactions according to the address sequence, and extracts the amount of each transaction in turn;

[0090] Step 2: Embed the amount into the key Convert to binary The data is divided into 8-bit segments, and the parity of each segment is calculated.

[0091] Step 3: The amount of each covert communication transaction and Each piece corresponds in sequence for testing. If the fragment is odd and the amount corresponding to the valid bit is odd, then the message binary is '1'; if the amount is even, then the message binary is '0', and vice versa.

[0092] Step 4: Extract the binary stream of the ciphertext hidden in each amount, concatenate them together, convert them to character form, and use the key. The decryption reveals the final hidden message "test".

[0093] In this embodiment, a blockchain covert communication system based on transaction amount is also provided to implement a blockchain covert communication method based on transaction amount. The system includes a sharing module, a message encryption module, a binary stream conversion module, a secret message embedding module, a blockchain transaction module, a covert transaction identification module, a decoding module, a character conversion module, and a message decryption module, wherein:

[0094] The sharing module is used to negotiate the seed key and shared address sequence between the message sender and the message receiver;

[0095] The message encryption module is used to encrypt secret information;

[0096] The binary stream conversion module is used to embed the encrypted secret message and amount into the key. Convert to a binary stream;

[0097] The secret message embedding module is used to embed a binary stream of a secret message into the transaction amount based on the amount embedding key.

[0098] The blockchain transaction module is used to construct and send blockchain transactions. It selects the address sequence and the amount generated in the secret message embedding module in sequence to construct and send the blockchain transaction.

[0099] The covert transaction identification module is used to identify blocks containing secret messages based on transaction addresses and sort them according to addresses;

[0100] The decoding module is used to decode the transaction amount and obtain the binary stream of the secret message;

[0101] The character conversion module is used to convert binary streams into characters;

[0102] The message decryption module is used to decrypt characters into plaintext messages.

[0103] like Figure 3 This embodiment provides a specific implementation process for a secret message embedding module, including the following steps:

[0104] 100. The first shift register is used to store the binary key. The second shift register is used to store the decimal part of the transaction amount, and the third shift register is used to store secret messages;

[0105] 101. Use the first shift register to store the binary key. And divide each group into 8-bit segments;

[0106] 102. Initialize i=1, j=1, k=1;

[0107] 103. Determine whether the j-th bit of the i-th key (i.e., the (i-1)×8+j-th bit in the first shift register) is 1. If it is not 1, proceed to step 104. If it is 1, proceed to step 106.

[0108] 104. Randomly select a number based on the probability of it appearing at the j-th position and store it in the second shift register (i.e., the (i-1)×8+j-th bit in the second shift register);

[0109] 105. Let j = j + 1;

[0110] 106. Determine if j is greater than 8. If it is, output eight digits from the second shift register and use these eight digits as the eight decimal places of the transaction amount. Set i = i + 1 and j = 1, and return to step 103. Otherwise, return directly to step 103.

[0111] 107. Obtain the parity of the decimal number corresponding to the i-th key, and if the number in the k-th bit of the third shift register is 1, select a number with the same parity as the decimal number corresponding to the i-th key and fill it into the (i-1)×8+j-th bit of the second shift register; otherwise, select a number with a different parity than the decimal number corresponding to the i-th key and fill it into the (i-1)×8+j-th bit of the second shift register.

[0112] 108. Determine whether all secret messages have been embedded. If so, end the process; otherwise, set k=k+1 and j=j+1, and execute step 106.

[0113] The second shift register is divided into eight-bit segments, and if there are fewer than eight bits, the final segment is output directly.

[0114] The message receiver identifies and retrieves transactions based on the addresses in the address sequence, sorts the transactions according to the address sequence, extracts the transaction amounts sequentially, and stores the sorted transaction amount sequence into the fourth shift register, such as... Figure 4 The decoding process includes the following steps:

[0115] 200. The fourth shift register is used to store the binary key. The fifth shift register is used to store the transaction amount, and the sixth shift register is used to store the output secret message;

[0116] 201. Use the first shift register to store the binary key. And divide each group into 8-bit segments;

[0117] 202. Initialize i=1, j=1, k=1;

[0118] 203. Determine whether the j-th bit of the i-th key (i.e., the (i-1)×8+j-th bit in the third shift register) is 1. If it is not 1, set j=j+1 and proceed to step 204. If it is 1, proceed to step 206.

[0119] 204. Determine if j is greater than 8. If not, return to step 203; otherwise, set i = i + 1 and j = 1, and return to step 103.

[0120] 205. The parity of the decimal number corresponding to the i-th key is determined. If it is the same as the j-th number of the i-th transaction amount, then the k-th bit of the sixth shift register is written with 1; otherwise, 0 is written.

[0121] 206. Determine whether all amounts have been decoded. If so, end the process; otherwise, set k=k+1 and j=j+1, and return to step 204.

[0122] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A blockchain-based covert communication method based on transaction amount, characterized in that, Specifically, the following steps are included: The message sender and receiver jointly negotiate a seed key, and then use a key expansion algorithm to expand the seed key into an amount embedding key. and share a set of address sequences; The message sender embeds the message into the transaction amount, specifically including: The private information is encrypted and converted into a binary stream, with the amount embedded in the key. Convert to binary stream ; The process of embedding a binary stream of a secret message into the transaction amount using a key embedded in the amount, and then transacting through the blockchain, includes: The first 8 digits of the transaction amount are used for message embedding, corresponding to the binary stream. The data is divided into slices, each slice being 8 bits. Determine each binary stream Find the corresponding decimal value and determine whether the value is parity. Each bit of the transaction amount is associated with a binary stream. Each bit is mapped to another, if the binary stream If a corresponding bit is 1, it indicates that the message is valid. If valid, then embed it into the binary stream at that bit. If the corresponding decimal values ​​are the same (odd or even), then embed them into the binary stream. The corresponding decimal values ​​of numbers with different parity; If binary stream If a corresponding bit is 0, it means that the message in that bit is invalid. A number is randomly selected as the bit for that position based on the frequency of the amount in the actual transaction. Select the next shard key and repeat the above steps until all private messages are embedded into the transaction amount. The message receiver obtains the transaction amount and extracts a hidden message from it. The process by which the message receiver extracts the hidden message from the transaction amount includes: The message receiver collects transactions containing secret messages from the blockchain based on a shared address sequence, sorts the transactions according to the address sequence, and extracts the transaction amount of each transaction in turn. Embedded key for amount Divide the data into segments, each segment consisting of eight digits, and sequentially correspond these segments to the eight decimal places of each amount. The current key value of 1 indicates that the corresponding bit is valid. If the current bit is valid and the parity of the decimal corresponding to the current chip key is the same as the parity of the corresponding transaction amount, then the value of this bit in the secret message is 1; otherwise, the value of this bit in the secret message is 0. The current key value is 0, indicating that the corresponding bit is invalid. Continue calculating the next bit.

2. The blockchain covert communication method based on transaction amount according to claim 1, characterized in that, The message sender and message receiver share the same set of address sequences. The message sender selects addresses as transaction addresses in the order of the address sequence to send secret messages. The message receiver identifies secret messages according to transaction addresses and sorts the transactions containing secret messages according to the order of the address sequences.

3. A blockchain-based covert communication system based on transaction amount, characterized in that, A blockchain covert communication method based on transaction amount as described in claim 1 includes a sharing module, a message encryption module, a binary stream conversion module, a secret message embedding module, a blockchain transaction module, a covert transaction identification module, a decoding module, a character conversion module, and a message decryption module, wherein: The sharing module is used to negotiate the seed key and shared address sequence between the message sender and the message receiver; The message encryption module is used to encrypt secret information; The binary stream conversion module is used to embed the encrypted secret message and amount into the key. Convert to a binary stream; The secret message embedding module is used to embed a binary stream of a secret message into the transaction amount based on the amount embedding key. The blockchain transaction module is used to construct and send blockchain transactions. It selects the address sequence and the amount generated in the secret message embedding module in sequence to construct and send the blockchain transaction. The covert transaction identification module is used to identify blocks containing secret messages based on transaction addresses and sort them according to addresses; The decoding module is used to decode the transaction amount and obtain the binary stream of the secret message; The character conversion module is used to convert binary streams into characters; The message decryption module is used to decrypt characters into plaintext messages.

4. A blockchain-based covert communication system based on transaction amount according to claim 3, characterized in that, In the secret message embedding module, the process of embedding the encrypted binary stream of the secret message into the transaction amount based on the amount embedding key includes: The first 8 digits of the transaction amount are used for message embedding, corresponding to the binary stream. The data is divided into slices, each slice being 8 bits. Determine each binary stream Find the corresponding decimal value and determine whether the value is parity. Each bit of the transaction amount is associated with a binary stream. Each bit is mapped to another, if the binary stream If a corresponding bit is 1, it indicates that the message is valid. If valid, then embed it into the binary stream at that bit. If the corresponding decimal values ​​are the same (odd or even), then embed them into the binary stream. The corresponding decimal values ​​of numbers with different parity; If binary stream If a corresponding bit is 0, it means that the message in that bit is invalid. A number is randomly selected as the bit for that position based on the frequency of the amount in the actual transaction. Select the next shard key and repeat the above steps until all private messages are embedded into the transaction amount.

5. A blockchain-based covert communication system based on transaction amount according to claim 3, characterized in that, The decoding module includes the following process: Decoding the transaction amount and obtaining the secret message. The message receiver collects transactions containing secret messages from the blockchain based on a shared address sequence, sorts the transactions according to the address sequence, and extracts the transaction amount of each transaction in turn. Embedded key for amount Divide the data into segments, each segment consisting of eight digits, and sequentially correspond these segments to the eight decimal places of each amount. The current key value of 1 indicates that the corresponding bit is valid. If the current bit is valid and the parity of the decimal corresponding to the current chip key is the same as the parity of the corresponding transaction amount, then the value of this bit in the secret message is 1; otherwise, the value of this bit in the secret message is 0. The current key value of 1 indicates that the corresponding bit is invalid; continue calculating the next bit.

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