diff --git a/wingle/src/main/java/kr/co/wingle/member/dto/MemoRequestDto.java b/wingle/src/main/java/kr/co/wingle/member/dto/MemoRequestDto.java
index 2fd2c986..088213c5 100644
--- a/wingle/src/main/java/kr/co/wingle/member/dto/MemoRequestDto.java
+++ b/wingle/src/main/java/kr/co/wingle/member/dto/MemoRequestDto.java
@@ -7,7 +7,7 @@
 @Getter
 public class MemoRequestDto {
 	@NotNull(message = "사용자 id가 없습니다.")
-	private Long userId;
+	private String userId;
 	@NotNull(message = "메모가 없습니다.")
 	private String memo;
 }
diff --git a/wingle/src/main/java/kr/co/wingle/member/dto/RejectionRequestDto.java b/wingle/src/main/java/kr/co/wingle/member/dto/RejectionRequestDto.java
index e5558a44..db82a07a 100644
--- a/wingle/src/main/java/kr/co/wingle/member/dto/RejectionRequestDto.java
+++ b/wingle/src/main/java/kr/co/wingle/member/dto/RejectionRequestDto.java
@@ -10,7 +10,7 @@
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
 public class RejectionRequestDto {
 	@NotNull(message = "사용자 id가 없습니다.")
-	private Long userId;
+	private String userId;
 	@NotNull(message = "거절 사유가 없습니다.")
 	private String reason;
 }
diff --git a/wingle/src/main/java/kr/co/wingle/member/dto/SignupResponseDto.java b/wingle/src/main/java/kr/co/wingle/member/dto/SignupResponseDto.java
index 198e28ef..698fb16c 100644
--- a/wingle/src/main/java/kr/co/wingle/member/dto/SignupResponseDto.java
+++ b/wingle/src/main/java/kr/co/wingle/member/dto/SignupResponseDto.java
@@ -7,11 +7,11 @@
 @Getter
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
 public class SignupResponseDto {
-	private Long id;
+	private String id;
 	private String name;
 	private String nickname;
 
-	public static SignupResponseDto of(Long id, String name, String nickname) {
+	public static SignupResponseDto of(String id, String name, String nickname) {
 		SignupResponseDto responseDto = new SignupResponseDto();
 		responseDto.id = id;
 		responseDto.name = name;
diff --git a/wingle/src/main/java/kr/co/wingle/member/service/AuthService.java b/wingle/src/main/java/kr/co/wingle/member/service/AuthService.java
index 2abe8016..0c4b8f93 100644
--- a/wingle/src/main/java/kr/co/wingle/member/service/AuthService.java
+++ b/wingle/src/main/java/kr/co/wingle/member/service/AuthService.java
@@ -18,6 +18,7 @@
 import kr.co.wingle.common.exception.NotFoundException;
 import kr.co.wingle.common.jwt.TokenInfo;
 import kr.co.wingle.common.jwt.TokenProvider;
+import kr.co.wingle.common.util.AES256Util;
 import kr.co.wingle.common.util.RedisUtil;
 import kr.co.wingle.common.util.S3Util;
 import kr.co.wingle.common.util.SecurityUtil;
@@ -50,6 +51,7 @@
 import kr.co.wingle.member.mailVo.CodeMail;
 import kr.co.wingle.member.mailVo.RejectionMail;
 import kr.co.wingle.profile.ProfileRepository;
+import kr.co.wingle.profile.ProfileUtil;
 import kr.co.wingle.profile.entity.Profile;
 import lombok.RequiredArgsConstructor;
 
@@ -67,6 +69,8 @@ public class AuthService {
 	private final RedisUtil redisUtil;
 	private final MailService mailService;
 	private final MemberService memberService;
+	private final ProfileUtil profileUtil;
+	private final AES256Util aes;
 
 	@Transactional
 	public SignupResponseDto signup(SignupRequestDto request) {
@@ -87,10 +91,16 @@ public SignupResponseDto signup(SignupRequestDto request) {
 		getTermAndSaveTermMember(member, TermCode.TERMS_OF_PROMOTION, request.isTermsOfPromotion());
 
 		// save profile
-		Profile profile = Profile.createProfile(member, request.getNickname(), request.isGender(), request.getNation());
+		if (profileUtil.isDuplicatedNickname(request.getNickname())) {
+			throw new DuplicateException(ErrorCode.DUPLICATE_NICKNAME);
+		}
+
+		Profile profile = Profile.createProfile(member, request.getNickname(), request.isGender(),
+			request.getNation());
 		profileRepository.save(profile);
 
-		return SignupResponseDto.of(member.getId(), member.getName(), profile.getNickname());
+		// encrypt and return
+		return SignupResponseDto.of(aes.encrypt(member.getId().toString()), member.getName(), profile.getNickname());
 	}
 
 	@Transactional
@@ -182,7 +192,7 @@ public PermissionResponseDto sendAcceptanceMail(AcceptanceRequestDto acceptanceR
 
 	@Transactional
 	public PermissionResponseDto sendRejectionMail(RejectionRequestDto rejectionRequestDto) {
-		Long userId = rejectionRequestDto.getUserId();
+		Long userId = Long.parseLong(aes.decrypt(rejectionRequestDto.getUserId()));
 		Member member = memberService.findMemberByMemberId(userId);
 		if (member.getPermission() == Permission.DENY.getStatus())
 			throw new CustomException(ErrorCode.ALREADY_DENY);
diff --git a/wingle/src/main/java/kr/co/wingle/member/service/MemberService.java b/wingle/src/main/java/kr/co/wingle/member/service/MemberService.java
index d091d4a5..68afec5e 100644
--- a/wingle/src/main/java/kr/co/wingle/member/service/MemberService.java
+++ b/wingle/src/main/java/kr/co/wingle/member/service/MemberService.java
@@ -10,6 +10,7 @@
 import kr.co.wingle.common.constants.ErrorCode;
 import kr.co.wingle.common.exception.ForbiddenException;
 import kr.co.wingle.common.exception.NotFoundException;
+import kr.co.wingle.common.util.AES256Util;
 import kr.co.wingle.member.MemberRepository;
 import kr.co.wingle.member.dto.MemoRequestDto;
 import kr.co.wingle.member.dto.MemoResponseDto;
@@ -27,6 +28,7 @@
 public class MemberService {
 	private final MemberRepository memberRepository;
 	private final ProfileRepository profileRepository;
+	private final AES256Util aes;
 	private final int pageSize = 10;
 
 	@Transactional(readOnly = true)
@@ -71,14 +73,15 @@ public WaitingUserResponseDto getWaitingUserInfo(Long userId) {
 
 	@Transactional
 	public MemoResponseDto saveMemo(MemoRequestDto memoRequestDto) {
-		Member member = findMemberByMemberId(memoRequestDto.getUserId());
+
+		Member member = findMemberByMemberId(Long.parseLong(aes.decrypt(memoRequestDto.getUserId())));
 		member.setMemo(memoRequestDto.getMemo());
 		return MemoResponseDto.from(memoRequestDto.getMemo());
 	}
 
 	@Transactional
 	public RejectionResponseDto saveRejectionReason(RejectionRequestDto request) {
-		Member member = findMemberByMemberId(request.getUserId());
+		Member member = findMemberByMemberId(Long.parseLong(aes.decrypt(request.getUserId())));
 		member.setRejectionReason(request.getReason());
 		return RejectionResponseDto.from(request.getReason());
 	}
diff --git a/wingle/src/main/java/kr/co/wingle/profile/ProfileService.java b/wingle/src/main/java/kr/co/wingle/profile/ProfileService.java
index cb6e610f..0a6d741b 100644
--- a/wingle/src/main/java/kr/co/wingle/profile/ProfileService.java
+++ b/wingle/src/main/java/kr/co/wingle/profile/ProfileService.java
@@ -13,7 +13,6 @@
 import kr.co.wingle.common.constants.ErrorCode;
 import kr.co.wingle.common.exception.DuplicateException;
 import kr.co.wingle.common.exception.NotFoundException;
-import kr.co.wingle.common.util.AES256Util;
 import kr.co.wingle.common.util.S3Util;
 import kr.co.wingle.member.entity.Member;
 import kr.co.wingle.member.service.AuthService;
@@ -46,7 +45,7 @@ public class ProfileService {
 	private final InterestRepository interestRepository;
 	private final SnsRepository snsRepository;
 	private final S3Util s3Util;
-	private final AES256Util aes;
+	private final ProfileUtil profileUtil;
 
 	@Transactional
 	public ProfileResponseDto saveProfile(ProfileRequestDto request) {
@@ -57,7 +56,7 @@ public ProfileResponseDto saveProfile(ProfileRequestDto request) {
 		Profile profile = getProfile(member);
 
 		if (!profile.getNickname().equals(request.getNickname()) &&
-			profileRepository.existsByNickname(request.getNickname())) {
+			profileUtil.isDuplicatedNickname(request.getNickname())) {
 			throw new DuplicateException(ErrorCode.DUPLICATE_NICKNAME);
 		}
 
diff --git a/wingle/src/main/java/kr/co/wingle/profile/ProfileUtil.java b/wingle/src/main/java/kr/co/wingle/profile/ProfileUtil.java
new file mode 100644
index 00000000..e4663d33
--- /dev/null
+++ b/wingle/src/main/java/kr/co/wingle/profile/ProfileUtil.java
@@ -0,0 +1,23 @@
+package kr.co.wingle.profile;
+
+import org.springframework.stereotype.Component;
+
+import kr.co.wingle.common.constants.ErrorCode;
+import kr.co.wingle.common.exception.DuplicateException;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+@RequiredArgsConstructor
+@Component
+public class ProfileUtil {
+	private final ProfileRepository profileRepository;
+
+	public boolean isDuplicatedNickname(String newNickname) {
+		if (profileRepository.existsByNickname(newNickname)) {
+			throw new DuplicateException(ErrorCode.DUPLICATE_NICKNAME);
+		}
+
+		return false;
+	}
+}