A method of processing a secure financial transaction, comprising: receiving a transaction request to complete a financial transaction, with at least a portion of the request encrypted according to a lattice-based Fully Homomorphic Encryption (FHE), said encrypted portion of the transaction request comprising confidential cardholder data comprising a primary account number (PAN), non-confidential cardholder data and transaction data; retrieving one or more sets of encrypted comparison cardholder data from a cardholder data database, each set of encrypted comparison cardholder data encrypted according to the lattice-based Fully Homomorphic Encryption (FHE); comparing the encrypted confidential cardholder data to each set of the encrypted comparison cardholder data using one or more homomorphic operations to determine which set of comparison cardholder data matches the confidential cardholder data and validating the confidential cardholder data, without decrypting the encrypted confidential cardholder data or the encrypted comparison cardholder data, wherein comparing the encrypted confidential cardholder data to each set of the encrypted comparison cardholder data includes comparing the encrypted PAN to each set of encrypted comparison PAN data; generating and encrypting an indicator indicating authorization or rejection of the request to complete the financial transaction based upon at least the validation of the confidential cardholder data; and forwarding the encrypted indicator indicating authorization or rejection of the request to complete the financial transaction to a party seeking authorization to complete the financial transaction, and wherein the confidential cardholder data is never decrypted during the method. receiving a transaction request to complete a financial transaction, with at least a portion of the request encrypted according to a lattice-based Fully Homomorphic Encryption (FHE), said encrypted portion of the transaction request comprising confidential cardholder data comprising a primary account number (PAN), non-confidential cardholder data and transaction data; retrieving one or more sets of encrypted comparison cardholder data from a cardholder data database, each set of encrypted comparison cardholder data encrypted according to the lattice-based Fully Homomorphic Encryption (FHE); comparing the encrypted confidential cardholder data to each set of the encrypted comparison cardholder data using one or more homomorphic operations to determine which set of comparison cardholder data matches the confidential cardholder data and validating the confidential cardholder data, without decrypting the encrypted confidential cardholder data or the encrypted comparison cardholder data, wherein comparing the encrypted confidential cardholder data to each set of the encrypted comparison cardholder data includes comparing the encrypted PAN to each set of encrypted comparison PAN data; generating and encrypting an indicator indicating authorization or rejection of the request to complete the financial transaction based upon at least the validation of the confidential cardholder data; and forwarding the encrypted indicator indicating authorization or rejection of the request to complete the financial transaction to a party seeking authorization to complete the financial transaction, and wherein the confidential cardholder data is never decrypted during the method. <EOS>